Newton’s

Three Laws

of Motion

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.

Sir Isaac Newton

(January 1643 – March 1727)

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

Newton’s First Law of Motion

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.

Newton’s First Law of Motion

Newton’s First Law of Motion

Inertia is a resistance to change in motion.

Newton’s First Law of Motion AKA The Law of

Inertia

Can You Explain…

Newton’s First Law of Motion

An object at rest will remain at rest…

DemosNewton’s First Law of Motion

Table Cloth Trick

Newton’s First Law of Motion

Can You Explain…

Newton’s First Law of Motion

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

For Example…

The Story of Fluffy

Newton’s First Law of Motion

Poor Baby Barbie

Newton’s First Law of Motion

http://www.physicsclassroom.com/mmedia/newtlaws/cci.cfm

Anti-Inertia Belts

Newton’s First Law of MotionBetter known

as “Seatbelts” !

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.

Newton’s 2nd Law of Motion

Newton’s 2nd Law of MotionThis 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 2nd Law of MotionForce = mass x

acceleration

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.

Newton’s 2nd 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.

Newton’s 2nd Law of Motion

Newton’s 2nd Law of Motion

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

Newton’s 2nd Law of Motion

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.

Newton’s 2nd Law of Motion

Newton’s 2nd Law of Motion

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.

Momentum

Momentum

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

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.

Law of Conservation of Momentum

• 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.

Law of Conservation of Momentum

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

Law of Conservation of Momentum& Newton’s 3rd

Law can be explained…

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.

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

Newton’s 3rd

Law of Motion

http://science.discovery.com/interactives/literacy/newton/newton.html

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