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Physical QuantitiesCard 1: What are physical quantities?
Physical Quantities1. A physical quantity is a quantity that can be measured.
2. A physical quantity can be divided into base quantity and derived quantity.
Card 2: What are base quantities?
Base Quantities
Base quantities are quantities that cannot be defined in term of other physical
quantities.
TopCard 3: State the 5 base quantities and their SI unit
5 Base Quantites
Quantity Name of Unit Symbol of Unit
Length metre m
Time second s
Temperature Kelvin K
Mass kilogram kg
Current Ampere A
Card 4: What is derived quantities?
Derived Quantities
A derived quantity is a Physics quantity that is not a base quantity. It is the quantities
which derived from the base quantities through multiplying and/or dividing them.
TopCard 5: What is derived unit?
Derived Unit
The derived unit is a combination of base units through multiplying and/or dividing
them.
Card 6: What are prefixes?
Prefixes
Prefixes are the preceding factor used to represent very small and very large physical quantities in
SI units.
Prefixes Symbol Value
Tera T 1012
Giga G 109
Mega M 106
kilo k 103
desi d 10-1
centi c 10-2
mili m 10-3
micro µ 10-6
nano n 10-9
pico p 10-12
fento f 10-15
TopCard 7: What are scalar quantities?
Scalar Quantities1. Scalars are quantities which are fully described by a magnitude alone.
2. Examples of scalar quantities are distance, speed, mass, volume,
temperature, density and energy.
Card 8: What are vector quantities?
Vector Quantities1. Vectors are quantities which are fully described by both a magnitude and a
direction.
2. Examples of vector quantities are displacement, velocity, acceleration, force,
momentum, and magnetic field.
Error analysisCard 1: What is error?
Error
Error is the difference between the actual value of a quantity and the value obtained
in measurement.
TopCard 2: What is systematic error?
Systematic Error
Systematic errors are errors which tend to shift all measurements in a systematic
way so their mean value is displaced. Systematic errors can be compensated if the
errors are known.
TopCard 3: State 3 sources of systematic error.
Sources of Systematic Error1. zero error, which cause by an incorrect position of the zero point,
2. an incorrect calibration of the measuring instrument.
3. consistently improper use of equipment.
TopCard 4: State 2 precaution steps to reduce systematic error.
Steps to reduce Systematic Error1. Conducting the experiment with care.
2. Repeating the experiment by using different instruments.
TopCard 5: What is meant by zero error?
Zero Error1. A zero error arises when the measuring instrument does not start from
exactly zero.
2. Zero errors are consistently present in every reading of a measurement.
3. The zero error can be positive or negative.
TopCard 6: Define random Error
Random Error1. Random errors arise from unknown and unpredictable variations in
condition.
2. It changes from one measurement to the next.
TopCard 7: State the causes of random error
Causes of Random Error
Random errors are caused by factors that are beyond the control of the observers.
Random error can cause by:
1. personal errors such as human limitations of sight and touch.
2. lack of sensitivity of the instrument: the instrument fail to respond to the
small change.
3. natural errors such as changes in temperature or wind, while the experiment
is in progress.
4. wrong technique of measurement.
TopCard 8: How random error can be avoided or reduced?
How to avoid random error1. Taking repeat readings
2. Find the average value of the reading.
TopCard 9: What is parallax error?
Parallax Error
A parallax error is an error in reading an instrument due to the eye of the observer
and pointer are not in a line perpendicular to the plane of the scale.
Card 1: What is meant by precision?
Precision
Precision is the ability of an instrument in measuring a quantity in a consistent
manner with only a small relative deviation between readings.
TopCard 2: How to measure the precision of a measurement?
Relative Deviation
The precision of a reading can be indicated by its relative deviation.
The relative deviation is the percentage of mean deviation for a set of
measurements and it is defined by the following formula:
TopCard 3: Define accuracy.
Accuracy
The accuracy of a measurement is the approximation of the measurement to the
actual value for a certain quantity of Physics.
TopCard 4: How the accuracy of a measurement can be increased?
How to Increase Accuracy1. taking a number of repeat readings to calculate the mean value of the
reading.
2. avoiding the end errors or zero errors.
3. taking into account the zero and parallax errors.
4. using more sensitive equipment such as a vernier caliper to replace a ruler.
Card 5: What is meant by sensitivity of a measuring instrument?
Sensitivity1. The sensitivity of an instrument is its ability to detect small changes in the
quantity that is being measured.
2. Thus, a sensitive instrument can quickly detect a small change in
measurement.
3. Measuring instruments that have smaller scale parts are more sensitive.
4. Sensitive instruments need not necessarily be accurate.
Card 6: Describe how a micrometer is used to make a measurement.
Micrometer Screw Gauge1. Turn the thimble until the object is gripped gently between the anvil and
spindle.
2. Turn the ratchet knob until a "click" sound is heard. This is to prevent
exerting too much pressure on the object measured.
3. Take the reading.
Reading of main scale = 5.5mm
Reading of thimble scale = 0.27mm
Actual Reading = 5.5mm + 0.27mm = 5.77mm
Scientific InvestigationCard 1: Scientific Report
Scientific Report
A report of the investigation must include:
1. Objective of the experiment,
2. Inference,
3. Hypothesis,
4. Three types of variables: manipulated variable, responding variable and
fixed variable,
5. Defined operational variables,
6. List of apparatus,
7. Procedure,
8. Tabulation of data,
9. Analysis of data,
10. Conclusion.
TopCard 2: What is meant by inference?
Inference
Inference is a statement to state the relationship between two visible quantities
observed in a diagram or picture.
TopCard 3: What is meant by hypothesis?
Hypothesis
Hypothesis is a statement to state the relationship between two measurable
variables that can be investigated in a lab.
TopCard 4: State the 3 variables that need to be control in a scientific investigation?
Variables
A variable is a quantity that can vary in value. There are 3 types of variable:
1. Manipulated Variables: Manipulated variables are factors which changed for
the experiment.
2. Responding Variables: Responding variables are factors which depend on
the manipulated variables.
3. Constant Variables: Constant variables are factors which are kept the same
throughout the experiment.
TopCard 5: Tabulating Data
Tabulating Data
A proper way of tabulating data should include the following:
1. The name or the symbols of the variables must be labelled with respective
units.
2. All measurements must be consistent with the sensitivity of the instruments
used.
3. All the values must be consistent to the same number of decimal places.
Card 6: Drawing graph.
Drawing Graph
Graphs are used to make a relationship between variables. Gradient value and
extrapolation of a graph are used to analyse a graph.
A well-plotted must contain the following features:
1. A title to show the two variables under investigation,
2. two axes labelled with the correct variables and their respective units,
3. the graph drawn is greater than 50 % of the graph paper,
4. appropriate scales (1:1 x 10x, 1:2 x 10x and 1:5 x 10x)
5. all the points are correctly plotted,
6. a best fit line is drawn
Top
2 Force and MotionLinear MotionCard 1: Linear Motion
Linear Motion
Linear motion is the movement of an object along a straight line.
Card 2: What is distance?
Distance
The distance traveled by an object is the total length that is traveled by that object.
Unit: metre (m)
Type of Quantity: Scalar quantity
Card 3: What is Displacement?
Displacement
Displacement of an object from a point of reference, O is the shortest distance of
the object from point O in a specific direction.
Unit: metre (m)
Type of Quantity: Vector quantity
Previous | Top | NextCard 4: What is the difference between distance and displacement?
Distance vs Displacement
Distance travelled = 200m
Displacement = 120 m, in the direction of Northeast
Distance is a scalar quantity,
Displacement is a vector quantity
Previous | Top | NextCard 5: What is speed
Speed
Speed is the rate of change in distance.
Formula:
Unit: ms-1
Type of quantity: Scalar quantity
Previous | Top | NextCard 6: What is velocity
Velocity
Velocity is the rate of change in displacement.
Formula:
Unit: ms-1
Type of quantity: Vector quantity
Previous | Top | NextCard 7: What is acceleration?
Acceleration
Acceleration is the rate of velocity change.Acceleration is a vector quantity
Formula:
Unit: ms-2
Type of quantity: Vector quantity
Previous | Top | NextCard 8: Notes - Acceleration
Notes - Acceleration An object moves with a constant velocity if themagnitude and direction of
the motion is always constant.
An object experiences changes in velocity if
o the magnitude of velocity changes
o the direction of the motion changes.
An object that experiences changes in velocityis said to have acceleration.
An object traveling with a constant acceleration,a, if the velocity changes at a
constant rate.
Previous | Top | NextCard 9: 4 Equations for Uniform Acceleration Motion
4 Equations of Uniform Acceleration
The above equation is for solving numerical problems involving uniform
acceleration.
Previous | Top | NextCard 10: Summary of the equation
Summary
Previous | Top
Ticker TapeCard 1: Ticker Timer
Ticker Timer
A ticker-timer consists of an electrical vibrator which vibrates 50 times per
second.
This enables it to make 50 dots per second on a ticker-tape being pulled
through it.
The time interval between two adjacent dots on the ticker-tape is called one
tick.
One tick is equal to 1/50 s or 0.02 s.
Top | NextCard 2: Analysing Ticker Tape 1 - Uniform Velocity
Uniform Velocity
The distance of the dots is equally distributed.
All lengths of tape in the chart are of equal length.
The object is moving at a uniform velocity.
Previous | Top | NextCard 3: Analysing Ticker Tape 1 - Uniform Acceleration
Uniform Acceleration
The distance between the dots increases uniformly.
The length of the strips of tape in the chart increase uniformly.
The velocity of the object is increasing uniformly, i.e. the object is moving at a
constant acceleration.
Previous | Top | NextCard 4: Analysing Ticker Tape 1 - Uniform Deceleration
Uniform Deceleration
The distance between the dots decreases uniformly.
The length of the strips of tape in the chart decreases uniformly.
The velocity of the object is decreasing uniformly, i.e. the object is
decelerating uniformly.
Previous | Top | NextCard 5: Finding velocity from ticker tape
Finding Velocity
Velocity of a motion can be determined by using ticker tape through the following
equation:
Caution!:
t is time taken from the first dot to the last dot of the distance measured.
Previous | Top | NextExample 1
Diagram 2.4 shows a strip of ticker tape that was pulled through a ticker tape timer that vibrated at 50 times a second. What is the
a. time taken from the first dot to the last dot?b. average velocity of the object that is represented by the ticker tape?
Answer:
a. There are 15 ticks from the first dot to the last dot, hence
Time taken = 15 × 0.02s = 0.3s
b.Distance travelled = 15cm
$\begin{gathered} v = \frac{s}{t} \hfill \\ v = \frac{{15cm}}{{0.3s}} = 50cms^{ - 1} \hfill \\ \end{gathered} $ Card 6: Findng acceleration
Finding Acceleration
Acceleration of a motion can be determined by using ticker tape through the
following equation:
Caution!:
t is time taken from the initial velocity to the final velocity.
Previous | Top | NextExample 2
The ticker-tape in figure above was produced by a toy car moving down a tilted runway. If the ticker-tape timer produced 50 dots per second, find the acceleration of the toy car.
Answer:
In order to find the acceleration, we need to determine the initial velocity, the final velocity and the time taken for the velocity change.
Initial velocity,
u = \frac{s}{t} = \frac{{3cm}}{{0.02s}} = 150cms^{ - 1} v = \frac{s}{t} = \frac{{0.5cm}}{{0.02s}} = 25cms^{ - 1}
Time taken for the velocity change,t = (0.5 + 4 + 0.5) ticks = 5 tickst = 5 × 0.02s = 0.1s
Acceleration,
a = \frac{{v - u}} {t} = \frac{{25 - 150}} {{0.1}} = - 1250cms^{ - 1}Example 3
A trolley is pushed up a slope. Diagram above shows ticker tape chart that show the movement of the trolley. Every section of the tape contains 5 ticks. If the ticker-tape timer produced 50 dots per second, determine the acceleration of the trolley.
Answer:
In order to find the acceleration, we need to determine the initial velocity, the final velocity and the time taken for the velocity change.
Initial velocity,
u = \frac{s}{t} = \frac{{5cm}}{{5 × 0.02s}} = 50cms^{ - 1} v = \frac{s}{t} = \frac{{1cm}}{{5 × 0.02s}} = 10cms^{ - 1}
Time taken for the velocity change,t = (2.5 + 5 + 5 + 5 + 2.5) ticks = 40 tickst = 40 × 0.02s = 0.8s
Acceleration,
a = \frac{{v - u}}
{t} = \frac{{10 - 50}} {{0.8}} = - 50cms^{ - 1}
Graph of Motion
Card 1: Displacement - Time Graph
Displacement - Time Graph
In a Displacement-Time Graph, the gradient of the graph is equal to the velocity of
motion.
Top | Next
Card 2: Analysign Displacement - Time Graph
Analysing Displacement - Time Graph
Gradient = 0Hence, velocity = 0
Gradient is constant,hence, velocity is Uniform
Gradient is negative and constant, hence velocity is uniform and in opposite direction
Gradient is increasing, hence velocity is increasing.
Gradient is decreasing, hence velocity is decreasing.
Previous | Top | Next
Card 3: Velocity - Time Graph
Velocity - Time Graph
The gradient of the velocity-time gradient gives a value of the changing rate
in velocity, which is theacceleration of the object.
The area below the velocity-time graph gives a value of the
object's displacement.
Previous | Top | Next
Card 4: Analysing Velocity - Time graph
Analysing Velocity - Time Graph
Uniform velocity Uniform acceleration
Uniform deceleration Increasing acceleration
Increasing deceleration
Previous | Top | Next
Card 5: Converting a Velocity-Time graph to Acceleration-Time graph
Converting a Velocity-Time graph to Acceleration-Time graph
In order to convert a velocity-time graph to acceleration time graph, we need to find
the gradient of the velocity time graph and plot it in the acceleration-time graph.
Previous | Top | Next
Card 6: Graph of free falling 1-Dropping an object from high place
Dropping an object from high place
Velocity - Time Graph Acceleration - Time Graph
Previous | Top | Next
Card 7: Graph of free falling 2 - Launching obejct upward
Launching Object Upward
Velocity-Time Graph Acceleration-Time Graph
Previous | Top | Next
Card 8: Graph of free falling 3 - Object moving upward and fall back to the ground
Object moving upward and fall back to the ground
Velocity-Time Graph Acceleration-Time Graph
Previous | Top | Next
Card 9: Graph of free falling 4 - Object falling and bounces back
Object falling and bounces back
Velocity-Time Graph Acceleration-Time Graph
Mass and Inertia
Card 1: What is mass?
Mass
Mass is the amount of matter.
Unit: kilogram (kg)
Type of quantity: Scalar quantity
Top | NextCard 2: What is inertia?
Inertia
Inertia is the property of a body that tends to maintain its state of motion.
Previous | Top | NextCard 3: State Newton's First Law
Newton's First Law
In the absence of external forces, an object at rest remains at rest and an object
in motioncontinues in motion with a constant velocity(that is, with a constant
speed in a straight line).
Previous | Top | NextCard 4: Situation Involving Inertia 1 - Jerking a Card
Jerking a Card
When the cardboard is jerked quickly, the coin will fall into the glass.
Explanation:
The inertia of the coin resists the change of its initial state, which is stationary.
As a result, the coin does not move with the cardboard and falls into the glass
because of gravity.
Previous | Top | NextCard 5: Situation Involving Inertia 2 - Pulling a Book
Pulling a Book
When the book is pulled out, the books on top will fall downwards.
Explanation:
Inertia tries to oppose the change to the stationary situation, that is, when the book
is pulled out, the books on top do not follow suit.
Previous | Top | NextCard 6: Situation Involving Inertia 3 - Pulling a Thread
Pulling a Thread
Pull slowly - Thread A will snap.
Explanation:
Tension of thread A is higher than string B.
Tension at A = Weight of the load + Pulling Force
Yank quickly - Thread B will snap.
Explanation:
The inertia of the load prevents the force from being transmitted to thread A,
hence causing thread B to snap.
Previous | Top | NextCard 7: Relation ship between mass and inertia
Larger Mass - Greater Inertia
Bucket filled with sand is more difficult to be moved. It's also more difficult to be
stoppedfrom swinging.
Explanation:
Object with more mass offers a greater resistance to change from its state of
motion.
Object with larger mass has larger inertia to resist the attempt to change the
state of motion.
Previous | Top | NextCard 8: Empty Cart is easier to be moved
Empty cart is easier to be moved
An empty cart is easier to be moved compare with a cart full with load. This is
because a cart withlarger mass has larger inertia to resist the attempt to change
the state of motion.
Previous | Top | Next
Momentum
Card 1:What is momentum?
Momentum
Momentum is defined as the product of mass and velocity.
Formula:
Unit: kgms-1
Type of quantity: Vector
Top | NextExample 1
A student releases a ball with mass of 2 kg from a height of 5 m from the ground. What would
be the momentum of the ball just before it hits the ground?
Answer:
In order to find the momentum, we need to know the mass and the velocity of the ball right
before it hits the ground.
It's given that the mass, m = 2kg.
The velocity is not given directly. However, we can determine the velocity, v, by using the
linear equation of uniform acceleration.
This is a free falling motion,
The initial velocity, u = 0
The acceleration, a = gravirational acceleration, g = 10ms-2
The dispacement, s = high = 50m.
The final velocity = ?
From the equation
v2 = u2 + 2as
v2 = (0)2 + 2(10)(5)
v = 10ms-1
The momentum,
p = mv =(2)(10) = 20 kgms-1
Card 2: Principle of Conservation of Momentum
Principle of Conservation of Momentum
The principle of conservation of momentum states that in a system make out of
objects that react (collide or explode), the total momentum is constant if no
external force is acted upon the system.
Sum of Momentum Before Reaction
= Sum of Momentum After Reaction
Previous | Top | NextCard 3: Formula of Principle of Conservation of Momentum
Formula
Previous | Top | NextExample 2: Both objects are in same direction before collision.
A Car A of mass 600 kg moving at 40 ms-1 collides with a car B of mass 800 kg moving at 20 ms-
1 in the same direction. If car B moves forwards at 30 ms-1 by the impact, what is the velocity, v,
of the car A immediately after the crash?
Answer:
m1 = 600kg
m2 = 800kg
u1 = 40 ms-1
u2 = 20 ms-1
v1 = ?
v2 = 30 ms-1
According to the principle of conservation of momentum,
m1u1 + m2u2 = m1v1 + m2v2
(600)(40) + (800)(20) = (600)v1 + (800)(30)
40000 = 600v1 + 24000
600v1 = 16000
v1 = 26.67 ms-1
Example 3: Both objects are in opposite direction before collision.
A 0.50kg ball traveling at 6.0 ms-1 collides head-on with a 1.0 kg ball moving in the opposite
direction at a speed of 12.0 ms-1. The 0.50kg ball moves backward at 14.0 ms-1 after the
collision. Find the velocity of the second ball after collision.
Answer:
m1 = 0.5 kg
m2 = 1.0 kg
u1 = 6.0 ms-1
u2 = -12.0 ms-1
v1 = -14.0 ms-1
v2 = ?
(IMPORTANT: velocity is negative when the object move in opposite siredtion)
According to the principle of conservation of momentum,
m1u1 + m2u2 = m1v1 + m2v2
(0.5)(6) + (1.0)(-12) = (0.5)(-14) + (1.0)v2
-9 = - 7 + 1v2
v2 = -2 ms-1
Card 4: What is elastic collision?
Elastic Collision
Elastic collision is the collision where the kinetic energy is conserved after the
collision.
Total Kinetic Energy before Collision
= Total Kinetic Energy after Collision
Additional notes:
-In an elastic collision, the 2 objects seperated right after the collision, and
-the momentum is conserved after the collision.
Previous | Top | NextCard 5: What is inelastic collision?
Inelastic Collision
Inelastic collision is the collision where the kinetic energy is not conserved after the
collision.
Additional notes:
-In a perfectly elastic collision, the 2 objects attach together after the collision, and
-the momentum is also conserved after the collision.
Previous | Top | NextExample 4: Perfectly Inelastic Collision
A lorry of mass 8000kg is moving with a velocity of 30 ms-1. The lorry is then accidentally
collides with a car of mass 1500kg moving in the same direction with a velocity of 20 ms-1.
After the collision, both the vehicles attach together and move with a speed of velocity v. Find
the value of v.
Answer:
(IMPORTANT: When 2 object attach together, they move with same speed.)
m1 = 8000kg
m2 = 1500kg
u1 = 30 ms-1
u2 = 20 ms-1
v1 = v
v2 = v
According to the principle of conservation of momentum,
m1u1 + m2u2 = m1v1 + m2v2
(8,000)(30) + (1,500)(20) = (8,000)v+ (1,500)v
270,000 = 9500v
v = 28.42 ms-1
Card 6: Application of conservation of momentum 1 - Rocket
Rocket1. Mixture of hydrogen and oxygen fuels burn in the combustion chamber.
2. Hot gases are expelled through the exhausts at very high speed .
3. The high-speed hot gas produce a high momentum backwards.
4. By conservation of momentum, an equal and opposite momentum is
produced and acted on the rocket, pushing the rocket upwards.
Previous | Top | NextCard 7: Application of conservation of momentum 1 - Jet Engine
Jet Engine1. Air is taken in from the front and is compressed by the compressor.
2. Fuel is injected and burnt with the compressed air in the combustion
chamber.
3. The hot gas is forced through the engine to turn the turbine blade, which
turns the compressor.
4. High-speed hot gases are ejected from the back with high momentum.
5. This produces an equal and opposite momentum to push the jet plane
forward.
Effects of Force
Card 1: Newton's Second Law
Newton's Second Law
The rate of change of momentum of a body isdirectly proportional to
the resultant force acting on the body and is in the same direction.
Implication:
When there is resultant force acting on an object, the object
will accelerate (moving faster, moving slower or change direction).
Top | NextCard 2: Force
Force A force is push or pull exerted on an object.
Force is a vector quantity that has magnitude and direction.
The unit of force is Newton ( or kgms-2).
Previous | Top | NextCard 3: Formula of Force
Formula of Force
From Newton's Second Law, we can derived the equation
(IMPORTANT: F Must be the net force)
Previous | Top | NextCard 4: Summary of Newton's 1st Law and 2nd Law
Summary of Newton's 1st Law and 2nd Law
Newton's First Law:
When there is no net force acting on an object, the object is either stationary or
move with constant speed in a straight line.
Newton's Second Law:
When there is a net force acting on an object, the object will accelerate.
Previous | Top | NextExample 1
A box of mass 150kg is placed on a horizontal floor with a smooth surface; find the acceleration
of the box when a 300N force is acting on the box horizontally.
Answer:
F = ma
(300) = (150)a
a = 2 ms-2
Example 2
A object of mass 50kg is placed on a horizontal floor with a smooth surface. If the velocity of
the object changes from stationary to 25.0 m/s in 5 seconds when is acted by a force, find the
magnitude of the force that is acting?
Answer:
We know that we can find the magnitude of a force by using the formula F = ma. The mass m
is already given in the question, but the acceleration is not give directly.
We can determine the acceleration from the formula
\begin{gathered}
a = \frac{{v - u}}
{t} \hfill \\
a = \frac{{25 - 0}}
{5} = 5ms^{ - 2} \hfill \\
\end{gathered}
From the formula
F = ma = (50)(5) = 250N
The force acting on the box is 250N.
Card 5: Effects of Force
Effects of Force
When a force acts on an object, the effect can change the
size,
shape,
stationary state,
speed and
direction of the object.
Previous | Top | Next