Newton’s Laws of Motion

To get us started….

Sir Isaac Newton• Born in England in

1643

• Lived for 85 years

Newton’s First Law• 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.

--Also called “The Law of Inertia”

What is this unbalanced force What is this unbalanced force that acts on an object in motion?that acts on an object in motion?

• There are four main types of friction:• Sliding friction: ice skating• Rolling friction: bowling• Fluid friction (air or liquid): air or

water resistance• Static friction: initial friction when

moving an object

Newton’s First Law

Examples of Newton’s 1st Law

a) A car suddenly stops and you strain against the seat belt

b) When riding a horse, the horse suddenly stops and you fly over its head

c) The magician pulls the tablecloth out from under a table full of dishes

d) Lawn bowling on a cut and rolled lawn verses an uncut lawn

e) A car turns left and you appear to slide to the right

Newton’s Second Law

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

If you place a force on an object, 1. It accelerates in the direction…that you push it2. If you push twice as hard…It accelerates twice as much.3. If it gets twice the mass…It accelerates half as much.

What does it mean?

Newton’s Second Law

Newton’s Third Law

• For every action, there is an equal and opposite reaction.

Newton’s Third Law

Example #1:

Action: Baseball pushes glove to the left

Reaction: ????

Example #1 Answer:

•The glove pushes the baseball to the right.

Example #2:

• Action: Bowling ball pushes pin to the left

• Reaction: ????

Example #2 Answer:

•Pin pushes bowling ball to the right.

Example #3:• Consider the

interaction depicted below between foot A, ball B, and foot C. Identify the two pairs of action-reaction forces. Use the symbols "foot A", "foot C", and "ball B" in your statements.

Example #3 Answer:

1. The first pair of action-reaction force pairs is: foot A pushes ball B to the right; and ball B pushes foot A to the left.

2. The second pair of action-reaction force pairs is: foot C pushes ball B to the left; and ball B pushes foot C to the right.

Challenge Question:

• Can you identify AT LEAST FIVE sets of action-reaction pairs in

the picture?

Challenge Answer:1. The elephant's feet push backward on the ground;

the ground pushes forward on its feet. 2. 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.

3. The left end of the right rope pulls rightward on the man; the man pulls leftward on the left end of the right rope.

4. The right end of the left rope pulls leftward on the man; the man pulls rightward on the right end of the left rope.

5. The tractor pulls leftward on the right end of the left rope; the left end of the left rope pulls rightward on the tractor.

Some Real-Life Applications of Newton's Third Law

1. An athlete executes a high jump by pushing against the earth which, in turn, pushes him/her up in the air.

2. We swim by pushing against the water, which reacts, propelling us ahead.

3. A helicopter rises because of the reaction to the downward push against the air produced by its propellers.

4. Water of high pressure hoses leaves the nozzle with great speed resulting in a thrust which pushes the hose with such force that one person cannot control it. Most people have experienced this to a much lesser degree with the garden hose.

Quiz Time:• Scenario #1

One foggy Christmas Eve, Santa's sleigh was so heavily laden with gifts for the good little boys and girls of LaVergne that the jolly old fellow had to employ his reserve reindeer, Clyde and Bubba, to assist the other eight members of his team. It took the combined force of the ten powerful animals to pull Santa's sleigh up into the starlit sky.

• Scenario 2 As Santa's sleigh was pulled forward, faster and higher, a little stuffed brown bear fell undetected off the back of the sleigh. Some little child is going to be very disappointed.

• Scenario 3 Fortunately for LaVergne's children, Santa and his team arrived on time. Spying the first housetop, Santa maneuvered his team for a landing. Unbeknownst to him, the children who lived there had left a treat on the roof for Santa's reindeer. The reindeer saw the treat and raced as fast as they could for the yummy oats and berries. They glided in, then they stopped so quickly that Santa flew forward and bumped his head on the front of the sleigh. Obviously, he had forgotten to fasten his seat belt!