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Force and Newton’s Laws of Motion. BY: BRIANNA SHIELDS. DO NOW. 1. If a foam block and a brick are dropped from the roof of the school, which one will hit the ground first? 2. Where on Earth could you go to weigh the most?
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Force and Newton’s Laws of Motion BY: BRIANNA SHIELDS
DO NOW • 1. If a foam block and a brick are dropped from the roof of the school, which one will hit the ground first? • 2. Where on Earth could you go to weigh the most? • 3. When a pendulum is allowed to freely swing back and forth it eventually slows down. Why?
GOAL • To define force and give examples of it • To apply Newton’s Laws of Motion
Physics Current Event • Read the article “Fantastic Physics” from the Current Science magazine • Use the response starters on your ELA bookmark to write 3 RESPONSES to the article
Force 1. Any push or pull 2. Can do one of the following: Balance each other out Overpower one another Work together
Wind blowing on a flag • Push • A magnet attracting metal • Pull
Jet engine moving a plane • Push • Moon causing the tides • Pull
Nuclear explosion • Push • Proton and electron attracting • Pull
Blowing up a balloon • Push • Tug of war • Pull
Gravity • Pull • Closing a door • Push or pull
2 forces in the same direction get added together Defining Force
Example • Suppose you couldn't pull a wagon of rocks yourself, so a friend started pulling on it with you- the pulling forces of you and your friend would be going in the same direction so you add them together
2 forces - one going one way, one going the other are subtracted from one another Object will move in the direction that the larger force is pointed towards Defining Force - =
Example • If a girl pulls a wagon against you in the opposite direction, the forces would combine by subtraction- The wagon would move in the direction of the greater force Overall Mvmt
Equal but opposite forces cancel eachother out Defining Force O
Example • If a girl pulls a wagon against you in the opposite direction, the forces would combine by subtraction- The wagon would move in the direction of the greater force No movement
Try the Force Examples on your handout • Draw a picture of each scenario • Label the forces with vectors (arrows) and amounts of force • Calculate the total force • Show the final direction of movement (if there is any) • When your group is finished, raise your hand and I’ll check your answers
Newton’s First Law of Motion An object in motion will stay in motion, an object at rest will stay at rest, unless acted on by a force FIRST LAW
Newton’s Second Law of Motion A force accelerates in the direction of the force & is related to the object’s mass F= ma SECOND LAW
Newton’s Third Law of Motion For every action, there is an equal but opposite reaction (forces come in pairs) THIRD LAW
Which Law of Motion? • When riding in a car that stops suddenly, your body keeps moving forward. First
Which Law of Motion? • The force of friction acts against an object’s motion. Third
Which Law of Motion? • When you’re driving fast on a straight road and then go around a sharp curve, why does everyone in the car bump into eachother or the doors and walls? First
Which Law of Motion? • You are pushing a cart in the grocery store. The more force you apply (the harder you push) the greater the cart accelerates. A full cart requires a greater force to accelerate. Second
Which Law of Motion? Third
Which Law of Motion? Third
Which Law of Motion? • The “kickback” of a gun on your shoulder while shooting it Third
Which Law of Motion? • As you walk, your feet push on the floor and the floor pushes back on you Third
Which Law of Motion? • Pulling a tablecloth out from beneath dishes without upsetting the dishes First
Which Law of Motion? First
Which Law of Motion? • While stepping off a boat, the boat pushes away from you. Third
Which Law of Motion? • If you are standing on a bus that suddenly moves forward, you are thrown off balance. Why? First
Which Law of Motion? • Why does a small car get better gas mileage? Second
Which Law of Motion? • How much force is needed to accelerate a 1400 kg car 2 m/s/s? Second
Which Law of Motion? First
Which Law of Motion? • Push on a desk- even if it doesn’t move you should have a mark on you hand. The harder you push on it, the harder it pushes back Third
Which Law of Motion? • Holding a bucket- you arm is holding it up, at the same time that gravity is pulling it down Third
Assessment • Use the formula F= ma to solve the following problem: A go-cart has a 140kg person in it. How much force would be required to accelerate the go-cart at 3m/s/s?
Assessment • In your lab groups, come up with one of your own examples for each of the three laws of motion: • Newton’s 1st law of motion • Newton’s 2nd law of motion • Newton’s 3rd law of motion