CHAPTER 3 MOTION

Contents:

1. Rest, Motion and Types of MOTION. 2. distance and Displacement

3. Speed, velocity, Acceleration and Types with Equations of motion4. Acceleration due to gravity and equation 5. Laws of motion.6. Tension and two special cases

7. motion inclined plane 8. LINEAR Momentum and Momentum in terms of second law of motion9. LAW OF CONSERVATION OF MOMENTUM

10. Elastic, INELASTIC collision. & Elastic collision on one dimension 11. EQUATIONS 12. DIMENSIONS

13. SHORT QUEASTIONS AND ANSWERS Classical Mechanics: Classical Mechanics is a part of Physics and describes the behavior of bodies with forces acting upon them. Classical Mechanics is often referred to as "Newtonian Mechanics" as Newton formulated the fundamental laws of motion on which Classical Mechanics is based. Classical Mechanics is divided into: Statics - studies of objects at rest.Kinematics - studies of objects in motion, without considering the forces acting upon them.

Dynamics - studies of motion under influence of force.

TECHNICAL TERM RELATIVE DEFINITIONS 1. Frame of Reference:While we observe a body that does not change its position with flow of time, we almost unknowingly refer to a second body which is nearby the first one. The second body should be a fixed one - it may be a domestic building or a tree, a lamppost or a prominent spot oh a road or a fixed star in the sky. This second body is called a reference body or a frame of reference. 2. Rest:A body is said to be at rest if it does not change its position with time from a fixed neighboring object.3. Motion:A body is in motion, if its position from a fixed neighboring object changes with time. In physics we are concerned with three types of motion: i) Translational or Linear.ii) Rotational or Angular.iii) Vibration or Oscillatory. A car moving down a highway is an example of translational motion, the Earths spin on its axis is an example of rotational motion, and the back-and-forth movement of a pendulum is an example of vibration motion.

4. Rest and motion are relative:A body seems to be at rest with respect to one neighboring fixed object but the same body may appear to be in motion with respect to some other fixed neighboring object So, rest and motion are relative terms. 5. Distance:The distance of a body is defined as its change in position. Distance is a scalar quantity; it is the path between two distinct poison points similar to one type of length in nature has unit meter and dimension [L].

6. Displacement:When an object changes its position as time passes on, the distance measured in the direction from its initial to final position along a straight line is known as its displacement.

Displacement is a vector quantity; it is directed from the initial position of a body to its final position. Unit in C.G.S system is cm and in M.K.S. system is m and dimension [L]. Thus, distance is the magnitude of displacement.7. Speed: Speed of an object, is the Total distance (d) traveled per Time (t) in straight line.

It is derived scalar quantity. The unit of speed in MKS system is m.sec-1 and dimension is [LT-1].8. Linear Velocity:The Velocity of an object is the rate of change of Displacement in time. The displacement (S) covered by a body in unit time (t) along straight line, is called its velocity or linear velocity. It is derived vector quantity.

The magnitude of velocity is, same as speed .The direction of velocity is same as the direction of displacement. The unit of velocity in MKS system is m.sec-1 and dimension is [LT-1]. Thus speed is the magnitude of velocity.

a) Uniform velocity: If the speed and direction of moving body does not change with time then its velocity is said to be uniform velocity.

b) Variable velocity:If the speed or direction changes with time then the velocity of such a body is said to be variable velocity.

c) Relative velocity:When two bodies are in motion the velocity of one body, relative to the other is called relative velocity.

d) Instantaneous velocity:Instantaneous velocity is the velocity at a given instant. Instantaneous velocity vinst equals the limiting value of the ratio as (t approaches zero: Instantaneous velocity is the derivative of displacement with respect to time.

9. Linear Acceleration:The continuously change of velocity of a body in unit time along straight line, is called its Linear acceleration or acceleration or it is the rate of change of velocity in time.

Thus,

The magnitude of acceleration is and its direction is same as the direction of velocity .The acceleration is derived vector quantity, of unit m. sec- in MKS system and dimension.

The continuous rate of increase of velocity in time is called positive acceleration (+ a). And continuous rate of decrease of velocity in time is called negative acceleration or retardation or deceleration (- a).

a) Instantaneous Acceleration: ( The continuous change of velocity of a body with time, as time approaches to zero is called Instantaneous acceleration.

Instantaneous acceleration is the derivative of velocity with respect to time

10. Equation of Motion: (For uniform motion,

For accelerated motion,

10. Acceleration due to gravity:Objects thrown upward or downward and those released from rest are all falling freely once they are released. Any freely falling object experiences change of velocity uniformly in unit time directed downward, regardless of its initial motion. Such acceleration is called acceleration due o gravity. We shall denote the magnitude of the free-fall acceleration by the symbol g. The value of g depends on altitude, at the Earths surface the value of g is approximately 9.80 m/s2.

Equations for acceleration due to gravity: (

11. Mass and weight: Mass is that property of an object that specifies how much inertia the object has, the SI unit of mass is the kilogram. The greater the mass of an object, the less that object accelerates under the action of an applied force. Mass is an inherent property of an object and is independent of the objects surroundings and of the method used to measure it. Also, mass is a scalar quantity.Weight is therefore an extrinsic property depending on the strength of gravitational acceleration to which a body is subjected and so would be smaller at the top of a mountain than at the mountain's bottom, while mass is an intrinsic property. Weight describes the pull of gravity on mass. In fact, it is the mass of the object times the acceleration due to the gravity acting on it. Weight, thus, is the gravitational force exerted on an object.

W = m g12. Forces:

The concept of the force is important to the development of mechanics and all of physics. A force is a "push" or "pull" experienced by a mass m when it is accelerated. The SI unit of force is the Newton, equal to 1 kg m s-2. The cgs unit of force is the dyne, and the British engineering unit of force is the pound. 13. Laws of Motion:The science of mechanics is based on three laws of motion, explained by Sir Isaac Newton, are also called Newtons laws of motion. First law of Motion: An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.Explanation:A glass of water placed on a table remains there unless a force is applied to remove it. Similarly, if a car is moving with uniform velocity, it goes on moving with the uniform velocity. Objects will remain in their state of rest or motion unless a force acts to change the motion. Any change in motion produces acceleration. This law is often called "the law of inertia". This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.Inertia of Rest and Inertia of Motion: Inertia of a body is its reluctance to change the state of rest or of uniform motion. It is also the degree of resistance a material body can offer to change of motion or rest condition. Inertia is of two types :(i) inertia of rest, (ii) inertia of motion. Inertia of rest: Inertia of rest is the inherent property of a material body by virtue of which it continues in its state of rest until and unless no external unbalanced force compels it to move. Inertia of motion: The tendency of a moving body to maintain its uniform motion in a straight line in absence of an effective external force is called inertia of motion Second law of Motion:The resultant force acting on a body will cause the body to accelerate in the direction of the resultant force. The acceleration of the body is directly proportional to the magnitude of the resultant force and inversely proportional to the mass of the object. Fnet ( a and

Therefore Fnet = m aExplanation:An external unbalanced force acts on a body then it generates acceleration in the direction of applied force. As force increases, acceleration also increases in the same direction along straight line, under constant mass. Mathematically:

The magnitude of force is given by, Force:

Force is, The product between mass and acceleration .It is a vector-derived quantity. Force is calculated in Newton and Dyne in metric system of units. Its dimension is [MLT].Newton:One kilogram mass produces an acceleration of 1m / sec2 in the direction of force then the force is called One Newton.

F = m a

Dyne: One gram mass produces an acceleration of 1cm / sec in the direction of force then the force is called One Dyne.

F = m a

Relation between Newton and Dyne: F = ma

1N = 105 dynes Third law of Motion:

Every action there is an equal and opposite reaction, differently bodies operate against each other with the forces directed along one straight line, equal on the module and opposite in a direction.Explanation:

Suppose a block exerts a force equal to its weight W on to a table, then it exerts an equal and opposite force called normal reaction R on to a block. Thus, Forces always occur in pairs.

DESCRIPTIVE PART

14. Tension in the string:"The force exerted by a string when a string is pulled", such force exerted by the string, on to the suspended body is called Tension in the string, denoted by T.Explanation:Consider a block of mass m which is suspended from a fixed beam by means of a string. The string is assumed to be light and inextensible. The string is stretched, since it is being pulled at both ends by the block and the beam. The string must be being pulled by oppositely directed forces of the same magnitude. By Newton's third law, the string exerts oppositely directed forces of equal magnitude T, on both the block and the beam. These forces act so as to oppose the stretching of the string, the beam experiences a downward force of magnitude T, whereas the block experiences an upward force of magnitude T. Where, T is termed the Tension of the string. Since T is a force, it is measured in Newtons. ( Calculation of Tension in the string and Acceleration in two unequal masses, when move vertically:Consider two masses, m1 and m2 connected by a light inextensible string which is suspended from a frictionless pulley. Let us assume that mass m1 is going to move downwards. The first mass is subject to an upward force T, due to the tension in the string, and a downward forcem1g , due to gravity. The net force cause the mass to move downwards with acceleration is, For the mass m1:

According to the second law of motion, F = m a, the unbalanced force acted on it is ( m1g T ).

Therefore, [m1 g T] = m1 a --------------eq. (1)

The second mass m2 is subject to a upward force, due to gravity m2 g, and an upward force T, due to the tension in the string. The net force cause the mass to move upward with acceleration is,

For the mass m2:According to the second law of motion, F = m a, the unbalanced force acted on it is (T m2 g).[T m2 g] = m2 a --------------eq. (2)Calculation of a:

By adding equations 1 and 2, we get,

[m1 g T] + [T m2 g] = (m1 a) + (m2 a)

m1 g m2 g = m1a + m2 a

g ( m1 - m2 ) = a ( m1 + m2 )

Calculation of T:

Divide equation 1 by equation 2,

m2 ( m1 g -T ) = m1 ( T- m2 g )

m2 m1 g - m2 T = m1 T - m1 m2 g

m1 m2 g + m1 m2 g = m1 T + m2 T

2 m1 m2 g =T (m1 + m2)

Show that, when m1= 3m2, while vertical motion.

Proof:

We know that,

, This shows that, vertical acceleration in two masses becomes one - half the acceleration due to gravity, when larger mass becomes three times the smaller mass.Show that W =T, When two bodies of equal masses suspended vertically. Proof:

Suppose, m1 = m2 and we know that,

T = m g

T = W This shows that, Tension in the string is equal to the weight of vertical suspended masses ( Calculation of Tension in the string and acceleration in two masses, while one mass moves vertically while the other horizontal:Consider two masses, m1 and m2, connected by a light inextensible string. Suppose that mass m2 slides over a smooth, frictionless, horizontal table, while the, massm1 is suspended over the edge of the table by means of a light frictionless pulley. No force is required to turn a frictionless pulley, so we can assume that the tension T of the string is the same on either side of the pulley. Let us apply Newton's second law of motion to each mass. The net forces cause the mass to move downwards with accelerationLet us derive expressions for calculating the a in the masses and T in the uniform string.

For the mass m1:According to the second law of motion, F = ma,

The net unbalanced force acting on it is (m1 g T).

m1 g T = m1 a --------------eq.(1) For the mass m2:According to the second law of motion, F = m a,

The unbalanced force is only T. Because, R (normal reaction force) = m2 g (weight of a body), balanced each other.

T = m2 a --------------eq. (2)

Calculation of a:

By adding equation 1 and 2, we get,

( m1 g T ) + T = m1 a + m2 a

m1 g = m1 a +m2 a

m1 g = a ( m1 + m2 )

Calculation of T:By putting the value of a in equation 2, we get,

Show that T1 = 2T2Proof:We know, , when two unequal masses move vertically.

And , when one mass moves vertically while the other horizontal.

By dividing both equations,

Thus,

We get, Thus, Tension in the string, when two unequal masses suspended at the ends of string move vertically is equal to the twice the tension; when one mass moves vertically while the other mass horizontal.

15. Friction:

When an object is pushed we feel some kind of resistance. A frictional force is created when the object has been given a tendency of motion. Therefore it acts in the opposite direction in order to resist the motion. Co-efficient of friction:The ratio of limiting friction (F) to the normal reaction force (W = m g = R) acting between two surfaces in contact is called the Co-efficient of friction, denoted by(. F = ( RLimiting friction:The force of friction is due to the roughness of material surfaces in contact. If the surfaces are smooth then there is no force of friction. The friction is self-adjusting force it does not increase indefinitely with the external force. If the body at the point of sliding then the force exerted called is Limiting force of friction. It is maximum value of static friction.Static Friction:

Static friction is the friction between two surfaces before they start moving against each other. This is the resistance that you feel when trying to slide a box across the floor. Before, the box starts moving; there is a resistance due to the static friction between the floor and box. Once the box starts moving, Fs = (s RKinetic Friction:

Kinetic friction takes over. Kinetic friction is the resistance between two rubbing surfaces. Through experience, most people know that it is harder to get the box moving compared to maintaining its motion. This is because static friction is always larger than kinetic friction. Fk = (k R Frictional forces depend on the types of surfaces on surfaces. These coefficients can equal one or zero and anything in between, but they cannot be greater than one or less than zero.Fluid Friction:The resistance to an object's motion through a fluid may be termed "Fluid Friction." It may take the form of viscous resistance in a liquid, or the rather different character of air friction when an object moves through a gas.

According to Stokes Law the, f = 6 ( ( r v

Where ( is the coefficient of viscosity and, r is the radius of the sphere moving with velocity v.

16. ( Motion on an inclined plane:A sloping plane, which makes an angle with the horizontal, is called, Inclined plane.Explanation:Consider a body of mass m is placed on an inclined surface making an angle ( with the horizontal. The weight (W) of a body is acting vertically downward, makes same angle with the normal reaction ( R ) . The weight is to be resolved in to its rectangular components, we get, W Cos( perpendicular and W Sin( parallel components to the inclined surface.

If the force of friction f opposes the motion of body then a body will remain in the state of rest, According to the first condition of equilibrium.

And

Suppose a body is sliding to wards the bottom point of slope, with acceleration a. A body is in the state of motion due to the, second law of motion. F = m a. The net unbalanced force acts on it is (m g Sin ( - f).

Thus, ( m g sin( - f ) = m a

We get,

If the force of friction is zero, (say f = 0),

Then,

This shows that, if force of friction is not present, then motion of a body is independent of mass of a body.

Special cases:

i) When, ( = 0o

Then, a = g sin 0oa = 0, (because, Sin 0o = 0). A body remains in the state of rest, on horizontal plane.

ii) When, ( = 60o

Then, a = g sin 60oa = g (0.5),

Thus, a = 4.9 m / sec2iii) When, ( = 90o

Then, a =g Sin 90o

a = g = 9.8 m / sec2, (because, Sin 90o = 1). A body falls freely, under the influence of gravity.

Above cases show that as the slope angle ( increases the motion a of body increases17. Linear momentum:Linear momentum is a measure of an object's translational motion.

The momentum depends on to Mass and Velocity of a body. It means,The product between mass and velocity of a body is called Momentum. Where, Linear

The linear momentum of a body of mass m moving with a velocity v is derived vector quantity. Its direction is same as the direction of velocity. The unit of momentum is N.sec or Kg .m /sec. And dimension is [M L-1 T-1]The magnitude of a linear momentum is, p = m v

Momentum in terms of second law of motion:Consider an object of mass m is moving with initial velocity vi has,

Initial momentum = m viAfter t seconds velocity becomes vf,

And, final momentum becomes = mvfHence, the change of momentum in t sec. = m vf m vi

Therefore, Rate of change of momentum = m a

Hence, Rate of change of momentum = F

This equation is for the second law of motion in terms of momentum that the rate of change of the linear momentum is equal to the net force acting on the body, is the second law of motion.

19. Impulsive force and Impulse:Impulsive force:The rate of change of momentum is called Impulsive force.

Its dimension is.When maximum force applied for very short time interval on to mass then,

Impulsive Force = Rate of change of momentum

Impulse:

The product between maximum force and short interval of time is called Impulse.

Its dimension is

Impulse = change of momentum20. ( Law of conservation of momentum

Total momentum before collision is equal to total momentum after collision of the isolated system remains conserved.Explanation:Consider two unequal masses m1 and m2 are moving with initial velocities U1, and U2 respectively along straight line in the same direction ( where U1 > U2). The total momentum before the head-on collision is (m1 U1+ m2 U2 ).The collision takes place in time t seconds, when the mass m1 collides with other mass m2. After this time the final velocities of the masses become V1 and V2. The total momentum after collision become ( m1 V1 + m2 V2 ). According to the second law of motion,

For the mass m1

And, For the mass m2.

According third law of motion, the force by mass m2 on to mass m1 is equal and opposite in the direction.

Hence.

, This is Law of conservation of momentum, Total initial momentum = Total final momentum.

This shows that, whenever two or more particles in an isolated system interact, the total momentum of the system remains constant. It is known as Law of conservation of momentum.

18. Elastic and Inelastic collision:Elastic collision:Total momentum before collision is equal to the total momentum after collision and total kinetic energy before collision is equal to the total kinetic energy after collision.It is called Elastic collision.

And, Inelastic collision:Total momentum before collision is equal to the total momentum after collision and total kinetic energy before collision does not equal to the total kinetic energy after collision. It is known as Inelastic collision.

And, 19. (Calculation of final velocities of two unequal masses after elastic collision:Consider two unequal masses m1 and m2 are moving with initial velocities U1 and U2 respectively, ( U1 > U2 ) in the same direction, on one dimension . The masses undergo an elastic head-on collision, in this case, both momentum and kinetic energy are conserved. Therefore, after the elastic collision the velocities of masses become V1 and V2. According to the law of conservation of momentum,

- - - - - - - - eq. 1

According to the law of conservation of kinetic energy,

- - - -- - - - eq. 2

Divide equation # 2 by equation #1, we get,

- - - - - - - - eq. 3From equation # 3 we get, - - - - - - - - eq. aAnd from equation # 3 we get, - - - - - - - - eq. bBy putting equation # (b) in equation # 1, we get,

EMBED Equation.DSMT4

By putting equation # (a) in equation # 1 we get,

Following are the special cases of elastic collision on one dimension. Case 1: Let, m1 = m2 = m. The masses m1 and m2 have initial velocities U1 and U2 respectively. After the collision the final velocities become,

Case 2: Let, m1 = m2 = m. A mass m1 is moving with velocity U1, other mass m is in the state of rest, say U2 = 0. After the collision the final velocities become,

Case 3: Let, mass m1 (( m2, say m1 and moving with U1. The larger mass m2 = m is in the state of rest, say U2 = 0. After the collision the final velocities become,

Case 4: Let, mass m1((m2 (say m1= m) moving with U1.And smaller mass m2 , is in the state of rest, say U2 = 0. After the collision the final velocities become,

Equations

mv/v=[force]=p/v=

Rate of Change of momentumF = ( R

M1U1+ M1U1= M2V2+ M2V2

p = m v

f = 6 ( ( r v

Latrecal Surface Volume =2rLVolume=LBwSurface Area=4r2

Latrecal Surface Volume =r2L

Dimensions

PHYSICAL QUANTITY SYMBOL DIMENSION UNIT

Distance or displacement d or s [L] m

Speed or velocity v = m s-1Acceleration a = m s-2Force or impulsive force F = = m a kg.ms-2 = Newton

Weight W mg kg.ms-2 = Newton

Mass m kg

Tension in string T = W kg.ms-2 = Newton

Momentum or impulse F (t p mv

EMBED Equation.DSMT4 kg.ms-1 = N.s

Viscosity ( kg.m-1.s-1Fluid friction f 6 r v kg.ms-2 = Newton

Density ( kg.m-3Pressure p kg.m-1.s-2 = N.m-2 =Pascal

Area A (lb) m2Volume V (lbh) m3Acceleration due to gravity g = m.s-2Coefficient of friction ( = no unit

Force density kg.m-2.s-2 = N.m-3Relative density = no dimension No unit

Specific volume kg-1.m3Surface tension kg.s-2

Short Questions and AnswersQ. No.1: Can a body moving at a constant speed have acceleration?When a body is moving in a circular path with a constant speed can have acceleration. In a circular path the direction of speed continuously changed but magnitude remains constant.Q. No.2: What is gravity? Explain the effect on the motion of free falling bodies.We know that earth attract every body to ward its center with a force, such force is called gravity.Hence, earth experiences an attractive force on every free falling bodies towards it center. Free falling bodies have zero initial velocity and positive acceleration due to gravity. And when thrown vertically upward freely than final velocity become zero and negative acceleration due gravity. These are the effect on free falling bodies.

Q. No.3: If a ball is thrown vertically upwards and the acceleration on it is neg 9.8 due to gravity will the sign change when the ball changes direction to fall back down thus giving an acceleration of 9.8?

Yes. On the way up, negative acceleration is taking place because the ball is moving up and gravity is acting in the opposite direction. On the way back down, acceleration is positive, and the object starts at rest. Yes. On the way up, negative acceleration is taking place because the ball is moving up and gravity is acting in the opposite direction. On the way back down, acceleration is positive, and the object starts at rest. Q. No.4: What is Inertia?The Inertia is a tendency of a body to remain in its original state. A body is in the state of rest will not change its state by it self or a body in the state of motion will not come to rest by itself. This is due to inertia. Q. No.5: Why the gun recoils, when a shell is fired from the gun?According to the third law of motion, every reaction is equal in magnitude but opposite in direction of action .So that gun applied action in forward direction and bullet experienced reaction in opposite direction. Thus, the gun recoils, when a shell is fired from the gun. Q. No.6: Define elastic collision and inelastic collision.Elastic collision: The Collision in which momentum and kinetics energy remain conserved is called elastic collision.

and

Inelastic collision: The collision in which momentum remains conserved and kinetic energy does not remains conserved .Such type of collision is called inelastic collision.

And

Q. No.7: Why moving bicycle is easy to stop but moving car is difficult to stop?Because, greater the momentum greater the mass or velocity, thus moving bicycle has smaller moment um than moving car. So that moving bicycle is easy to stop but moving car is difficult to stop.Q. No.8: What is the physical significance of momentum?The motion of moving body is the physical significance of momentum. Q. No 9: What do you know about fluid friction?The fluid friction is made to flow around a stationary object then friction produces itself. Such friction is involved in the ships through water and automobile through air. F= 6 r v Q. No.10: Find the mass of a body whose weight is 1960N.Answer: We know that, W = mg (

( m = 200 kg Q. No.11: Define a) Impulse b) law of conservation of momentum c) Impulsive force.

Impulse:

The product between maximum force and short time interval is called impulse. Fmax (t = mvf - mvi Impulse = Change of momentum

Law of conservation of momentum:

Total initial momentum before collision is equal to the total final momentum after collision, is called law of conservation of momentum.

M U1 + m U2 = M v1 + m v2 Impulsive force:The maximum force applied for very short time interval, is called impulsive force. Fmax = m vf- m vi (t

Impulsive force = Rate of change of momentum

Q. No.12: A block rests on an inclined plane. What forces act on it? Draw force diagram.A block rests on an inclined plane under first condition of equilibrium.( Fx = 0 and ( FY = 0Three forces are acting on to a body. One of them is the weight of a body, second one is the normal reaction force applied by inclined plane and third one is the force of friction opposes the motion of a body.

Q. #10: Differentiate between the mass and weight. MASS WEIGHT

1It is a quantity of a matterIt is not a quantity of matter

2It is fundamental quantity in the metric system. t is derived quantity

3Its units are kilogram and gram in metric systemIts unit is Newton and dyne in metric system.

4It is measured by physical balance. It is measured by spring balance.

5m = W/ g W = m g

6It is not a pull of gravity. It is a pull of gravity.

7It remains constant everywhere. It does not remain constant everywhere.

8It is fundamental quantity It is derived quantity.

Q. No.13: Define force and give its units.The force is an agent of pushing or pulling of any object. It depends on to mass of an object and accele4ation produced in it. Thus, F = m a Its unit is Newton and dyne in metric system.Q. No.14: Define coefficient of friction.The ratio between normal reaction force applied by the surface and limiting force is called coefficient of friction.( = F / RQ. No.15: Define static and kinetic friction.Friction is divided into two types-static and kinetic. These are represented by Fs, for static friction, and Fk, for kinetic friction. Static friction occurs when the body is not moving with respect to the surface. It is the force which makes it difficult to start something moving. On the other hand, kinetic friction occurs when the body is sliding over the surface. Rolling objects also experience friction. This is the force which causes objects to slow down and eventually stop. Friction is usually approximated as being proportional to the normal force. The proportionality constant is called the coefficient of static or kinetic friction. The coefficient is represented ass for static friction, andk for kinetic friction; the numerical value of depends on the nature of the surface with which the body is in contact.Q. No.16: What is SI unit of momentum?The unit of momentum in S.I. system is N.sec.Q. No.17: What do you mean by an isolated system?The isolated system means, a system having distinct boundaries through which no transformation of matter and energy.Q. No.18: It is well known that balancing a bicycle standing still is almost impossible, while on a rolling bike it is quite easy. Why?The natural tendency is to lean to the right, to counter balance the lean with your weight. But in moving the top of your body to the right, by Newton's 3rd law you are actually pushing the bike to lean more to the left. May be you should lean to the left and push the bike back? It might work for a fraction of a second, but now you are really out of balance. Circle of action and reaction.

Q. No.19: Why uniform circular motion is called accelerated motion? [Improve] If an object moves along a circular path, the only change in its velocity is due to the change in the direction of the motion. The motion of the object moving along the circular path is, which a uniform circular motion is, is therefore an accelerated motion.Q. No.20: What is the difference between uniform motion and uniformly accelerated motion? Uniform motion is constant acceleration non uniform is not.

What is uniformly accelerating linear motion? Linear motion Motion implies momentum, which implies velocity. Linear implies a straight line. Accelerating implies changing velocity. And uniform implies constancy.

So, when an object moves in a straight line and accelerates at a constant rate, you have uniformly accelerating linear motion.

Q. No.21: Describe the term inertia with respect to motion?

Every mass has inertia. When an inertial mass is in motion, it tends to continue to be at its state of motion obeying Newtons first law of motion. The law states that every body in this universe continues to be at the state of rest or motion until and unless acted by an external force. We experience inertia of motion when we are riding a vehicle in motion. When the vehicle tries to stop suddenly, we are jerked forward. This jerking is due to inertia of motion as our bodies try to continue to be at the state of motion in accordance to Newtons first law.Q. No.22: Balancing a bicycle standing still is almost impossible, while on a rolling bike it is quite easy. Why?Different principles are at work in each case. Suppose you sit on a bike that stands still, and find it is leaning to the left. What do you do? The natural tendency is to lean to the right, to counter balance the lean with your weight. But in moving the top of your body to the right, by Newton's 3rd law you are actually pushing the bike to lean more to the left. May be you should lean to the left and push the bike back? It might work for a fraction of a second, but now you are really out of balance. No way!On a rolling bike, balance is kept by a completely different mechanism. By slightly turning the handle bars right or left, you impart some of the rotation of the front wheel ("angular momentum") to rotate the bike around its long axis, the direction in which it rolls. That way the rider can counteract any tendency of the bike to topple to one side or the other, without getting into the vicious circle of action and reaction.

SIR ISAAC NEWTON QUOTESA man may imagine things that are false, but he can only understand things that are true, for if the things be false, the apprehension of them is not understanding. Isaac Newton

Errors are not in the art but in the artificers. Isaac Newton

I can calculate the motion of heavenly bodies, but not the madness of people. Isaac Newton

I was like a boy playing on the sea-shore, and diverting myself now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. Isaac Newton

If I have done the public any service, it is due to my patient thought. Isaac Newton

If I have seen further than others, it is by standing upon the shoulders of giants. Isaac Newton

It is the weight, not numbers of experiments that is to be regarded. Isaac Newton

Tact is the art of making a point without making an enemy. Isaac Newton

To every action there is always opposed an equal reaction. Isaac Newton

To me there has never been a higher source of earthly honor or distinction than that connected with advances in science. Isaac Newton

To myself I am only a child playing on the beach, while vast oceans of truth lie undiscovered before me. Isaac Newton

We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. Isaac Newton

We build too many walls and not enough bridges. Isaac NewtonFor More Notes Of Chemistry, Physics, English and Other Subjects Visit:

HYPERLINK "http://www.meustaad.blogspot.com"www.meustaad.blogspot.com

HYPERLINK "http://www.notesnotes4free.co.vu"www.notesnotes4free.co.vu

Prof: Najeeb Mughal, Edited by Tarvesh Kumar Page 16

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