Describe MOTION and CHANGES in motion. Newton's Laws Describe MOTION and CHANGES in motion.

The 3 Laws of Motion Law of Inertia Law of Acceleration Law of Action-Reaction

First Law of Motion Law of inertia Inertia- the tendency of an object to resist changes in motion. Objects at rest [not moving] will STAY at rest until an unbalanced FORCE acts on them Objects in motion will STAY in MOTION until an unbalanced force acts on them Objects with greater MASS have more INERTIA Bigger objects are harder to start and stop

Second Law of Motion Law of acceleration A FORCE is needed to CHANGE motion Objects ACCELERATE in the DIRECTION of the force The MORE FORCE applied, the greater the ACCELERATION The more MASS an object has, the more FORCE IS NEEDED to accelerate the object F=MA or A=F/M

F=MA or A=F/M

In other words… Acceleration & Force If using more force, there will be more acceleration (change in speed or direction) (mass is constant)

Acceleration & Mass The more mass, the less acceleration (force is constant)

Third Law of Motion Law of action-reaction FORCES occur in PAIRS The forces are EQUAL and OPPOSITE One force is an ACTION force The other force is a REACTION force The forces act on DIFFERENT objects

Other examples of Newton’s Third Law The baseball forces the bat to the left (an action); the bat forces the ball to the right (the reaction).

3rd Law Flying gracefully through the air, birds depend on Newton’s third law of motion. As the birds push down on the air with their wings, the air pushes their wings up and gives them lift.

Newton’s 3rd Law in Nature Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. In turn, the water reacts by pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards).

3rd Law The reaction of a rocket is an application of the third law of motion. Various fuels are burned in the engine, producing hot gases. The hot gases push against the inside tube of the rocket and escape out the bottom of the tube. As the gases move downward, the rocket moves in the opposite direction.

3rd Law Consider the motion of a car on the way to school. A car is equipped with wheels which spin backwards. As the wheels spin backwards, they grip the road and push the road backwards.

1. Jen is stepping out of a boat on to a dock 1. Jen is stepping out of a boat on to a dock. She has one foot on the dock and one foot in the boat. No one holds on to the boat. It begins to move away from the dock. Jen's legs split wider and wider. Which law applies?  

2. Jen is playing soccer. She kicks a goal from the 18 line with her left foot. Which law applies? 

3. Jen is using her computer. She bumps her mouse 3. Jen is using her computer. She bumps her mouse. It falls off the desk. Which law applies?

4. Jen goes shopping at the grocery store 4. Jen goes shopping at the grocery store. She notices that as she adds items to the cart it gets harder to push. Which law applies?

5. Jay is the defensive tackle on the football team 5. Jay is the defensive tackle on the football team. When he hits the other team's linemen, he bowls him over backwards. Which law applies?

6. Jay is in the lunch line pushing his tray along the tray ledge 6. Jay is in the lunch line pushing his tray along the tray ledge. He wants to hurry things, so he gives his tray a mighty push. John (who is 2 people ahead of Jay) sees his tray fly off the tray ledge and on to the floor. His buddy, Bits says, "Hey, that is a good example of ......”

7. The school has a magician give an assembly 7. The school has a magician give an assembly. He waves his hand over a table that has a tablecloth covering it. It is set with dishes and glasses. He suddenly yanks the tablecloth off, but all the dishes and glasses stay in place. Mike says, "That's magic!" Dr. Farr, the physics teacher, says, "Actually, that is a fine example of Newton's ..... law!”

8. Jay drives his truck to football practice. He gives Jen a ride 8. Jay drives his truck to football practice. He gives Jen a ride. The truck stalls in the parking lot. He gets out and pushes it, but it won't budge. He tells Jen to get out and help him push. They manage to push the truck into a parking space. (Thank goodness he is a lineman!) Which law applies?