1. Isaac Newton: cool dude
Biography of Newton

2. Isaac newton

3. Inertia What is inertia?
The tendency of an object to resist change
An object tends to stay still if it’s still, or stay moving if it’s moving
What do you have to do to get something to move?
Overcome inertia; apply an unbalanced force

4. Newton’s laws of motion
First Law:
An object in motion stays in motion, unless acted upon by an (unbalanced) net force. It will continue to move at constant speed in a straight line. An object at rest stays at rest, unless acted upon by an unbalanced (net) force.
Newton’s first law is also known as the “Law of Inertia”

9. Newton’s laws of motion
Remember that unbalanced forces cause acceleration (a change in velocity)
What factors determine how much an object will accelerate?
Amount of force, mass, and direction of force

11. What happens if you apply a big force and a small force to the same object?
The big force will accelerate it more

12. What happens if you apply the same force to objects with different masses?
The object with the smaller mass will be accelerated more

13. Bellringer
If you double (x2) the force you apply on an object, what will happen to its acceleration?

14. Newton’s laws of motion
Newton’s Second Law:
Force is related to an object’s mass and acceleration
F = ma
The greater the force, the greater the change in motion

18. Bellringer 2/26
When you hit a nail with a hammer, what is the action force? What is the reaction force?

19. Newton’s laws of motion
Third Law:
For every action force, there is an equal and opposite reaction force
Forces always act in pairs
The two forces act in opposite directions.
When you push on something, that is an action force. The object pushes back on you with a reaction force.

20. Action-reaction (Newton’s 3rd law)
When you bounce a basketball, what is the action force?
The ball hitting the floor
What is the reaction force?
The floor pushing back on the ball, causing it to bounce back
What happens when you increase the action force?
The reaction force also increases

21. Action-reaction (Newton’s 3rd Law)
How does a rocket work?
Rocket fuel is burned, which produces hot gases that expand rapidly and escape out of the back of the rocket. These escaping gases propel the rocket upward.
What is the action force?
The escaping gases
What is the reaction force?
The rocket moving up

22. Bellringer 3/2 Predict what will happen when I squeeze the bottle.
What do you observe?
Why do you think this is happening?

23. Name Newton’s 3 laws of motion.
bellringer
Name Newton’s 3 laws of motion.

24. Review
What’s Newton’s Laws Say?
Newton’s Laws & a bicycle

25. momentum What does momentum typically mean? Momentum = mass x velocity
Something that is on the move or hard to stop
Momentum = mass x velocity
Momentum is usually abbreviated as “p” and units are kg*m/s

26. momentum
How much momentum does a 0.1 kg baseball have if it is moving at 40m/s?
Momentum = M x V = 0.1kg x 40m/s = 4 kgm/s
How much momentum does a 1200 kg car have if it is also moving at 40 m/s?
Momentum = M x V = 1200 kg x 40m/s = 4800kgm/s

27. momentum The more momentum something has, the harder it is to stop
More mass, more momentum
Does an object at rest have momentum?
No—momentum is not the same as inertia
More velocity, more momentum
How do you increase velocity?
Apply a greater force

30. bellringer
Calculate the momentum of a 5 kg ice skater traveling at 8 m/s.
If a truck has a momentum of 5000 kgm/s and is driving at 100 m/s, what is its mass?

31. Momentum
How could an object with a larger mass have the same momentum as an object with a small mass?
If a 18-wheeler and bicycle are going at the same speed, which has more momentum?
What happens to a car’s velocity as it slows down?
What happens to its momentum?

32. momentum
If you are driving a bumper car and run into another bumper car, what happens to your momentum?
Your momentum transfers to the other car when you hit it

33. Conservation of momentum
Law of Conservation of Momentum: the total momentum of objects that interact does not change (momentum of system before = momentum of system after)
The total momentum of any group of objects remains the same (unless outside forces like gravity or friction act on them)
If the total momentum of 2 cars is 500 kgm/s before a collision, what is the total momentum of them after they collide?
Still 500 kgm/s

36. Bellringer 3/12
If the momentum of one bumper car is 40 kgm/s and the momentum of the other bumper car is 50 kgm/s, what is the total momentum of the whole system (both cars) before the collision?
What is the total momentum of both cars after the collision?

37. Bellringer 3/16 What causes the last ball to move?
Balloon Rocket Day 2 lab due today (Day 1 now past due)!
Quiz Wednesday on Newton’s Laws, Pressure, & Momentum!

38. Study guide for Wednesday’s quiz
Know: inertia, action/reaction, water pressure, law of conservation of momentum, buoyant force
Be able to use these equations (will not be given on quiz!):
Force = mass x acceleration
Pressure = force ÷ area
Momentum = mass x velocity

39. Newton’s cradle

42. collisions
“Non-Sticky” Collisions: when two objects hit and bounce off each other
If they are of different masses, they trade velocities
Car that had been going faster will slow down, car that had been going slower will speed up

45. collisions
“Sticky Collisions”: sometimes 2 objects of the same mass hit and continue moving together
After they collide, they share the momentum

46. Questions
More collisions
Car crash
Balloon in a van

47. Bellringer activity
Finish the statements on a separate sheet of paper:
An object in motion stays in motion unless ….
Every action has an …..
Fill in the blank (word bank: area, velocity, mass, force, inertia, acceleration)
The name for the tendency of an object to keep doing what it’s doing is ____________
The acceleration of an object depends on _________ and _________________
The momentum of an object depends on __________ and __________________
Pressure depends on ____________ and _____________
Less ___________, more pressure.
The momentum of a system before and after a collision is the same/less/more (write one).
An object floats if its buoyant force is equal/greater/less (write one) than the gravitational force.