Work
What is work, in the physics classroom sense?
W=F*d*cos(theta)
OR
A force does work on an object by acting during a certain distance. The amount of work done on a system changes the total energy of the system.
What is the equation for (gravitational) potential energy?
PE =m*g*h
What is the equation for kinetic energy?
K.E.= 1/2 mv^2
What does it mean that energy is conserved?
Energy cannot be created or destroyed.
Name three movies by Hayao Miyazaki
My Neighbor Totoro
Howl's Moving Castle
Spirited Away
Ponyo
Kiki's Delivery Service
Princess Mononoke
Suzie pushes a crate with 200 N of force across her 7-meter long living room. How much work does Suzie do on the crate?
Suzie does 1400 J of work.
Suzie brought a 3 kg crate to her apartment and did 795 J of work on it. How high is Suzie's apartment?
About 27 meters high.
Suzie does 230 J of work on a crate (2 kg) traveling on a flat icy surface. Assuming there is no friction, how fast is the crate going if it started from rest?
About 15 meters per second.
Consider the following roller coaster. Assuming the velocity of the cart is 0 m/s at the top of the very first hill, how fast is the cart going when it reaches the top of the first loop? Ignore friction.
About 11 m/s
Suzie is planning to climb Mount Kilimanjaro (5895 meters). There's a steep trail that will take 4 days, and a longer trail with a moderate slope that will take 6 days. She's trying to determine which one will require less power. What trail should she take?
Both trails require the same amount of work but the longer trail will require less power because it takes a longer amount of time.
Suzie is pulling a sled traveling at constant velocity with 40 N of force applied. She travels 58 meters to the start of the sledding hill. How much work is she doing on the sled?
About 2320 Joules
Suzie is planning to climb Mount Kilimanjaro (5895 meters). There's a steep (but short) trail, and a longer trail with a moderate slope. She's trying to determine which one will take more work. What trail should she take?
Both trails will require the same amount of work.
Suzie pushes a crate at constant speed doing 450 J of work on it. How fast is the crate going at the end of this, assuming the crate starts at 1 m/s?
1 m/s. The same speed as before since the the crate is moving AT CONSTANT SPEED.
Consider the following roller coaster. Assuming the velocity of the cart is 2 m/s at the top of the very first hill, how fast is the cart going when it reaches the top of the second loop? Ignore friction.
About 14 meters per second.
Bright Orange!
Suzie is pulling a sled traveling at constant velocity with 40 N of force applied. She travels 58 meters to the start of the sledding hill. How much work is friction doing on the sled?
About -2320 Joules (taking energy away from the system)
Consider the following roller coaster. What is the potential energy at the top of the very first hill?
About 73600 Joules.
Suzie pushes a crate (2 kg) from rest, doing 450 J of work on it, on a frictionless surface. How fast is the crate going at the end of this?
About 21 meters per second.
You brought your phone (137 grams) to the top of the Grand Canyon (1857 meters) to take pictures of the view, and you accidentally drop it when you get to the top. How fast is your phone going right before it hits the water? Assume you lose 200 J to air resistance.
About 183 meters per second!
According to the Hitchhiker's Guide to the Galaxy, what is the annwer to the ultimate question of life, the universe, and everything?
42
A 2300-kg truck traveling at 30 m/s comes to a complete stop. The truck experiences a net average force of 12500 N. How far (distance) did the truck travel before coming to a complete stop?
About 83 meters.
You brought your phone (137 grams) to the top of the Grand Canyon (1857 meters) to take pictures of the view. How much work did you do on the phone?
About 2500 Joules.
Suzie pushes a crate (2 kg), doing 450 J of work on it, on a frictionless surface. How fast is the crate going at the end of this, assuming the crate starts at 3 m/s?
About 11.6 meters per second.
Consider the following roller coaster. The velocity of the cart is 5 m/s at the top of the very first hill. By the time it gets to the end of the ride, it has lost 60% of the original energy. Will it be going faster, slower, or the same as when it started?
It will be traveling at almost 10 meters per second, faster than the 5 m/s it started with.
Consider the following roller coaster. The velocity of the cart is 2 m/s at the top of the very first hill. If I want the cart to stop as soon as it gets to the bottom of the second loop (after the loop itself), how much should the force of friction be through the 31 meter loop?
About 2400 Newtons!