Newton and his laws

Friction Paragraphs

• Hand up if you have it done

Newton

Life

• Scholar– Brilliant mind– Became Head of Oxford Colleges in England– Royal Society of England– Master everything in his age

• Teacher– Help to develop whole branch of Mathematics– Newtonian physics

• Alchemist

Newton’s laws of motion

• Clearly laid down the rules that govern why things move in our world

• Rules start falling apart when at microscopic scale or at high speeds

1st law of motion

• An object at ______, stays at ______

• An object in motion, stays at a _______ rate

Unless

A net outside ________ acts upon it.

How will their motion compare?

What forces effect their ability to roll down a hallway?

• Friction with ground

• Air Resistance

A bowling ball will move with nearly constant velocity

• No significant friction from the ground or air resistance to help change the bowling ball’s motion

A Tennis ball will slow down

• Both friction and air resistance has a greater effect on the ball.

• It has much less mass

Mass

• Mass of an object = the amount of material that makes up the object

• The more massive the object, the harder it is to change its motion

What Does Inertia mean?

The Res

Inertia is the measure of an object’s resistance to change in

motion

Inertia Trick

• Need– Weight (Washer), quarter– Cup– Index Card

Mass and Inertia

• The more massive an object, the more inertia it has

Sumo and inertia

American Sumo

Assignment for Wednesday

• Find 10 examples in life of objects demonstrating the first law

• 10 different objects, 10 different actions

• Denote if object is stopped, at constant velocity or accelerating

• If accelerating, indicate the cause

2nd Law of motion

• The amount of acceleration of an object is related to:– Its mass

• As mass increases, acceleration decreases

– The net force exerted on it• As net force increases, acceleration increases

a = Fnet

m

Fnet = m a

Units

• Some units that are made out of 2 or more fundamental units are renamed after a Famous Scientist

• Units of Force– 1 Kg (m/s2) = 1N (Newton)

Weight is a force

• Weight is the measure of the Force of gravity

• To find your weight in Newtons:

– Take your weight and divide it by 2.2

– Take the result and multiply it by 9.8

What weighs 1000 N?

Football player (220 lbs)

What weighs 100 N?

Freshman backpacks

What weighs 10 N?

The average textbook

What weighs 1 N?

A smallish apple

Homework in book

• What force is necessary to accelerate a 1250 kg car at a rate of 40 m/s2?

Answer?

• Have m, a

• Need F

• Use f = ma

• F= 1250 x 40 = 50,000 N

Question #2

• What is the mass of an object if a force of 34N produces an acceleration of 4 m/s2?

Answer #2

8.5 kg

Mathematical equation for Weight of an object

• Weight =

mass x acceleration due to gravity

On earth’s surface, acceleration due to gravity is = to 10 m/s2

Calculate your mass value

• Take your weight in Newtons and divide by 10

Acceleration due to gravity

• Paper and Book test

• Which drops faster?

• Any other forces at work besides gravity (weight)?

New Homework

• Page 369– Problems 22-29

Newton’s 3rd Law

• For every __________, there is an equal and opposite ________

• If the action force is a pen pressing against a piece of paper, then the reaction force is_______