Three Laws of MotionThree Laws of Motion

NEWTON’S THREE LAWS OF MOTION

NEWTON’S FIRST LAWNEWTON’S FIRST LAW

A BODY AT REST REMAINS AT REST AND A BODY IN

MOTION REMAINS IN UNIFORM MOTION IN A

STRAIGHT LINE UNLESS ACTED ON BY AN EXTERNAL

UNBALANCED FORCE

Newton’s First Law ExplainedNewton’s First Law Explained

Experience tells us that a stationary object remains at rest unless acted on by some outside force. We know that forces are necessary to cause anything to move if it is originally at rest.

Less obvious is the fact that an object in motion will continue in motion until an outside force changes the motion. For example, a rolling ball slows down until it stops rolling because of its interaction with the floor, called friction, between the floor and the ball. The ball will roll longer and farther in a smooth surface than in a rough one. This leads to the idea that if the surface is frictionless the ball will move forever. These ideas are part of Newton’s first law.

NEWTON’S SECOND LAWNEWTON’S SECOND LAW

The acceleration a of an object in the direction of a resultant force F, is directly proportional to the magnitude of the force and inversely proportional to the mass m

Answer this to illustrate the Answer this to illustrate the first law of motion.first law of motion.

In Enchanted In Enchanted kingdom, one of the kingdom, one of the rides was Jungle rides was Jungle Log Jam. During the Log Jam. During the descent of the car descent of the car from the top of the from the top of the rail, why did you rail, why did you pitch forward when pitch forward when the car slowed the car slowed down?down?

Newton’s Second Law Explained!Newton’s Second Law Explained!The Law of Acceleration:

Experience tells us that larger and larger resultant forces on the same object will result in greater and greater changes in the velocity of the object.

F 2F

a

2a

Furthermore:Furthermore:If we keep the resultant force constant and apply it to greater and greater masses, the change in velocity decreases. The change in velocity per init time is defined as its acceleration a. He demonstrated the direct relationship between the applied force and the resulting acceleration. He showed that the acceleration decreased proportionally with the inertia or mass of the object.

a = — or F = ma

Fm

m

2m

3mF

F

F

a

½ a

CONSTANT FORCE INCREASING MASS RESULTS IN DECREASING VELOCITY

?

1.

2.

3.

What would be the acceleration of no. 3?

We can deduce that:We can deduce that:

Acceleration, Acceleration, aa is directly is directly proportional to the proportional to the resultant resultant force, force, FF and inversely and inversely proportional to the proportional to the mass, mass, mm..

a = —F

m

NEWTON’S THIRD LAWNEWTON’S THIRD LAW

FOR EVERY ACTION THERE MUST BE AN EQUAL AND OPPOSITE REACTION FORCE

Newton’s Third Law ExplainedNewton’s Third Law ExplainedThere can be no force unless two bodies

are involved . When a hammer strikes a nail, it exerts an “action” force on the nail. But the nail must also “react” by pushing back against the hammer. In all cases, there must be an acting force and a reacting force. Whenever two bodies interact, the force exerted by the second body on the first (the reaction force) is equal in magnitude and opposite in direction to the force exerted by the first body n the second (the action force).

Illustrating the 3Illustrating the 3rdrd Law of Motion Law of Motion

The wheels of the car push on the road.

The road pushes the wheels of the car.

ACTION FORCE:

REACTION FORCE:

THANK YOU FOR LISTENING!THANK YOU FOR LISTENING!

That’s all folks. That’s all folks. Got it?Got it?