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Newton’s Three Laws of Motion

Sir Isaac NewtonSir Isaac Newton ((January 1643 – –March 1727) )

Newton's laws of motion are three physical laws which provide relationships between the forces acting on a body and the motion of the body.

Newton’s First Law… Newton’s First Law…

An object at rest will remain at rest- unless acted upon by an outside force.

Newton’s First LawNewton’s First Law

           An object in motion will remain in motion – unless acted upon by an outside force.

                           

Newton’s First Law of Motion

An object at rest remains at rest, and an object in motion remains in motion at a constant speed and in a straight line unless acted on by an unbalanced force.

Chapter 6

Newton’s First Law of Motion, continued

Chapter 6

The First Law is Also Called…The First Law is Also Called…

The Law of Inertia

Inertia is a resistance to change in motion.

Can You Explain ?Can You Explain ?

Examples…Examples…

An object at rest will remain at rest.

1. Activity # 1

2. “Freefall”

The Tablecloth TrickThe Tablecloth Trick

An object in motion will continue to move in a straight line.

For Example…

The Story of FluffyThe Story of Fluffy

Poor Baby BarbiePoor Baby Barbie

Anti- Inertia BeltsAnti- Inertia Belts

Better known as “Seatbelts” !

Newton’s Second Law of Motion

The acceleration of an object depends on the mass of the object and the amount of force applied.

• Newton’s second law describes the motion of an object when an unbalanced force acts on the object.

Chapter 6

Newton’s Second LawNewton’s Second Law

This Law shows the relationship between mass, force, and acceleration.

When a force is applied to a mass, it accelerates.

The larger the mass of an The larger the mass of an object, the more force needed object, the more force needed to start it, stop it, or change its to start it, stop it, or change its

direction.direction.

                

                          

A speeding bullet and a slow moving train both have tremendous force. The force of the bullet can be attributed to its incredible acceleration while the force of the train comes from its great mass.

Newton’s Second Law of Motion

The acceleration of an object depends on the mass of the object and the amount of force applied.

• Newton’s second law describes the motion of an object when an unbalanced force acts on the object.

Chapter 6

Newton’s Second Law of Motion

• Part 1: Acceleration Depends on Mass The acceleration of an object decreases as its mass increases. Its acceleration increases as its mass decreases.

• Part 2: Acceleration Depends on Force An object’s acceleration increases as the force on the object increases. The acceleration of an object is always in the same direction as the force applied.

Chapter 6

Chapter 6 Section 2 Newton’s Laws of Motion

Chapter 6 Section 2 Newton’s Laws of Motion

Newton’s Second LawNewton’s Second Law

For Example: A Bowling Ball vs a ping pong ball.

Or Runaway RampsOr Runaway Ramps

Choose Your Position..Choose Your Position..

Some Athletes are long and lean, with little body fat, and little muscle. Basketball players and wide receivers fit this category.

Choose Your Position…Choose Your Position…

Other athletes, on the other hand, have lots of body fat, lots of muscle, and gain weight easily. Football lineman and sumo wrestlers are heavier and rounder individuals

Momentum, Mass, and Velocity

• The momentum of an object is the product of the object’s mass and velocity. Object at rest has zero momentum.

Calculating Momentum The relationship of momentum (p), mass (m) in kilograms, and velocity (v) in meters per second, is shown in the equation below:

p m x v

What is (i) the total kinetic energy before the collision;(ii) the total kinetic energy after the collision.

(iii) the total loss in kinetic energy.

The Law of Conservation of Momentum

• The law of conservation of momentum states that any time objects collide, the total amount of momentum stays the same.

The Law of Conservation of Momentum

• The combined objects have a different velocity because momentum is conserved and depends on mass and velocity.

• So, when the mass changes, the velocity must change, too.

The Law of Conservation of Momentum, continued

• Objects Bouncing Off Each Other When two objects bounce off each other, momentum is transferred from one object to the other.

• The transfer of momentum causes the objects to move in different directions at different speeds.

The Law of Conservation of Momentum, continued

• Conservation of Momentum and Newton’s Third Law Conservation of momentum can be explained by Newton’s third law.

• Because action and reaction forces are equal and opposite, momentum is neither gained or lost in a collision.

Forces Always Come in PairsForces Always Come in Pairs

.

Newton’s Third Law of Motion

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite

force on the first.

• Newton’s third law of motion can be simply stated as follows: All forces act in pairs.

Newton’s Third LawNewton’s Third Law

For every action force, there is an equal, but opposite, reaction force.

The Action Force is Equal in The Action Force is Equal in size but Opposite in Direction.size but Opposite in Direction.

Action and Reaction forces Action and Reaction forces always act on different always act on different

objects.objects.

Action Force: The man pushes against the wall.

Reaction Force: the wall pushes on the man.

Newton's third law does not mean that forces always cancel out so that nothing can ever move. If these two figure skaters, initially at rest, push against each other, they will both move.

Another example: Recoil of a Another example: Recoil of a gun or cannongun or cannon

Or…Launching a RocketOr…Launching a Rocket

Or… a Lawn SprinklerOr… a Lawn Sprinkler