Balloon Rocket

Lab A Preview ofA Preview ofthe labthe labFridayFriday

After theAfter the

QuizQuiz

Science 7

Darren Nigh

Sir Isaac Newton’s Three

Laws of Motion

Isaac Newton• Born 1642• Went to University of Cambridge in England as a

student and taught there as a professor after• Never married• Gave his attention mostly to physics and

mathematics, but he also gave his attention to religion and alchemy

• Newton was the first to solve three mysteries that intrigued the scientists– Laws of Motion– Laws of Planetary Orbits– Calculus

Famous Quotes• If I have seen further it is

by standing on the shoulders of giants

• I can calculate the motion of heavily bodies but not the madness of people

• A man may imagine things that are false, but he can only understand things that are true

• To every action there is always opposed an equal reaction

Major Achievements• The invention, design and construction of a

reflecting telescope (1668) – He ground the mirror, built the tube, and even made his own

tools for the job -- The mirror gave a sharper image than was possible with a

large lens because a lens focuses different colors at slightly different distances, an effect called chromatic aberration. 

– This was a real advance in telescope technology, and ensured his election to membership in the Royal Society

• Newton realized that the moon’s circular path around the earth could be caused by the same gravitational force that would hold a fired cannonball in low orbit, in other words, the same force that causes bodies to fall. 

• His three Laws

Laws• The First Law

– Law of inertia – An object at rest stays at

rest objects in motion stays in motion

• The Second law – Law of acceleration – Force equals mass times

acceleration

• The Third law – Law of Interaction– For every action there is

an equal and opposite reaction

Three Laws of Motion

Newton’s First Law

The Law of Inertia Newton’s

Second Law The Law of

Acceleration

Newton’s Third Law The Law of Interaction

I. The 1st Law of Motion

Law of InertiaAn object at rest will remain at rest, and an object in motion will remain in motion with constant velocity unless acted upon by an external force.

In other words….

For example:

A boy stopping ball #1 or kicking ball #2 would be an outside force.

Outside Force:

When driving a car, the seat belt provides the unbalanced force which brings you from a state of motion to a state of rest.

Perhaps you could speculate what would occur when no seat belt is used.

• If the truck were to abruptly stop and the straps were no longer functioning, then the ladder in motion would continue in motion

II. The 2nd Law of Motion

The acceleration of an object increases with increased force and decreases with increased mass

Law of Acceleration

It accelerates in the direction that you push it.

If you push twice as hard, it accelerates twice as much.

If it receives twice the mass, it accelerates half as much.

For Example:

• A ball is in motion and it has a certain velocity (speed/acceleration) that it will maintain.

The ball’s velocity will change if acted upon by an outside force.

If the surface the ball is rolling on were to slant, the ball’s velocity would

change and the ball would move faster. The slant would be considered the

outside force.

III. The 3rd Law of Motion

Law of Interaction

In every action, there is always an equal and opposite reaction

As the man jumps off the boat, he exerts the force on the boat and the boat exerts the reaction force on the man.

The man leaps forward onto the pier, while the boat moves away from the pier.

Newton’s Third Law

The elephant's feet push backward on the ground; the ground pushes forward on its feet. The right end of the right rope pulls leftward on the elephant's body; its body pulls rightward on the right end of the right rope. The left end of the right rope pulls rightward on the man; the man pulls leftward on the left end of the right rope. The right end of the left rope pulls leftward on the man; the man pulls rightward on the right end of the left rope. The tractor pulls leftward on the right end of the left rope; the left end of the left rope pulls rightward on the tractor. etc., etc.

Click for more understanding.

up, up and

AWAY!

Let's study how a rocket works to understand Newton's Third

Law.

For Example:

• Imagine you are riding a skateboard…

Now imagine that you are not very good at riding the skateboard and

you fall forward…

According to Newton’s Third Law, as you fall in one direction, there is an

opposite reaction occurring in the other direction.

• Basically, as you fall forward, the skateboard will move in the other direction.

Instant Review---Laws• The First Law

– Law of inertia – An object at rest stays at

rest objects in motion stays in motion

• The Second law – Law of acceleration – Force equals mass times

acceleration

• The Third law – Law of Interaction– For every action there is

an equal and opposite reaction

Centripetal Force

• Any force that keeps an object moving in a circle is known as Centripetal Force.

• The force points toward the center of the circle

• Without Centripetal Force, the object would go flying off in a straight line

Momentum

• The momentum of an object is the product of its mass and velocity.

• At the same velocity a wrecking ball has more momentum then a tennis ball

• However, if you compare two wrecking balls of the same size, the faster wrecking ball has the most momentum.

Collision• A situation in which two objects in close

contact exchange energy and momentum• As another car bumps into the back of

yours, the force pushes your car forward.• Some of the momentum of the car behind

you is transferred to your car• At the same time the car behind you slows

because of the reaction force from your car

• You gain momentum and the other car loses momentum

ConclusionForces change motion

Objects at rest remain at rest, objects in motion remain in motion at the same velocity unless acted upon by an unbalanced force

Force and Mass determine acceleration

The acceleration of an object increases with increased force and decreases with increased mass

Forces act in pairs

When an object exerts force on another object, the second object exerts an equal and opposite force on the first object

Forces transfer momentum

Momentum is a property of a moving object

Forces in collisions are equal and opposite

Momentum is conserved in collisions