Objectives:
1) To learn about the overview of what
Newton did in his career
2) To learn about inertia

• Batman is trapped by the joker in the center of a frozen lake.
• The ice of this lake has no friction.
• It turns out with no friction you cannot walk/run
• How will batman save himself? Stay tuned…

• Newton was the father of theoretical physics!
• Had some mathematical discoveries such as calculus.
• Created “classical mechanics” – branch of physics.
• Used a prism to prove that white light was actually a combination of many colors of light – lead to his book on optics.
• Came up with his 3 laws of motion.

A body in rest stays at rest until acted upon by an outside force, and a body in motion remains in motion until acted upon by an outside force.

• Force is just the pushing or pulling on something.
• If you push on a door, that is a force on the door and by Newton’s first law, that door now has to change its motion (none) to a new motion (opening).

• You are in the center of a frozen lake which has no friction and is completely smooth and flat.
• Ignore wind resistance.
• You toss out a hockey puck at a speed of
1 mile per hour.
• How fast does the hockey puck go when it is close to the edge of the lake (assume the lake is 500 miles across)?

• You are in a space craft which is over a trillion miles from the closest star (so that means there is very little gravity on you) traveling at a speed of 2 miles per second.
• If you run out of “gas” so to speak, what will happen to your spacecraft and why?
• How far do you think you will go before you stop?

• One form of force is called “weight”.
• Weight is your total downwards force.
• In this case it is the earth pulling you down.
• Units of weight can be pounds or Newtons.
• Note that while your mass is the same anywhere you go, your weight is not.
• One way to loose weight without loosing any mass is to move to the equator.
• Since the earth spins there is an outward force – and this decreases your net downward force, which decreases your weight.

• The moon has 1/6 th the gravity of the earth.
• If you weighed 180 lbs on earth then how much would you weigh on the moon?
• If your mass on earth was 80 kg then what is your mass on the moon?

• Well, you apply a force.
• This force makes it accelerate.
• The stronger the force, the faster it accelerates.
• If an object is at rest, and you give it a force in the North direction, what direction will it move?
• If an object is moving North and you give it a force in the South direction and keep applying that force for a long time then what will happen to the object?

• I toss a ball in the North direction (giving it a force in that direction).
• Gravity pulls down on the ball.
• What will the motion of the ball be like?

• Note: net force is the sum of all forces.
• To add up forces they have to point in the same direction.
• Note that up = -down
• I stand on the ground.
• What is the net force on me (hint, is my velocity changing)?

• Gravity is pulling down on me with a force of about 1000 N.
• What pushes me upwards with a force of
1000 N and what would happen if this force suddenly went away?

• A supertanker has its engines locked in the on position but is headed for harbor.
• The supertanker’s engines proved force such that there is a forwards force of 1 million Newtons
• Ten tugboats tie themselves to the supertanker and push their engines to the max (100,000 Newtons) in the opposite direction.
• What is the net force on the supertanker?
• Will the supertanker stop before it runs into the shore?
• We will ignore air and water resistance for this question.

• We have learned that unless an object is pushed or pulled on, it will keep moving at a constant speed (and if that speed is 0, it stays put).
• So, for Batman to get off the frozen lake, he needs a force – but where oh where can he get that force from? Is Batman doomed to stay on that lake forever? Stay tuned….