Work
Kinetic and Potential Energy
Conservation of Energy
Power and Miscellany
Mr. Crawford Personal Trivia
100
A worker pushes a box 7 meters across the floor with 150 Newtons of force. How much work did he do?
1050 J
W=Fd=150*7=1050 Joules
100
An object at rest can have which type of energy?
Potential Energy
100
An apply hanging from a tree initially has 18 J of mechanical energy. If the apple falls from the tree, how much mechanical energy does it have right before it hits the ground?
18 J
Mechanical energy is conserved.
100
A crane does 130000 Joules of work in 100 seconds. What is the power of the crane?
130 Watts
P=W/t = 130000/100 = 130
100
What is Mr. Crawford's Wife's name (at school)?
Ms. Guy
200
A cook gets locked in the freezer at work. He pulls on the door as hard as he can (1100 N of Force) for 2 minutes before he has exhausted himself, but the door never moves. How much work did he do?
None! No displacement means no work was done.
200
A bird in flight has which type(s) of energy?
Kinetic and Potential Energy
200
A frictionless rollercoaster starts from rest at the top of a hill with 15000 J of potential energy. When the rollercoaster reaches the bottom of the lowest hill, does it have more than, less than, or exactly 15000 J of kinetic energy?
Exactly 15000 J of kinetic energy
200
What are the units of each of the following quantities.
1. Work
2. Energy
3. Power
4. Force
1. Joules
2. Joules
3. Watts
4. Newtons
200
Which dog belongs to Mr. Crawford?
Gracie!
300
If a student does 1200 J of work to climb up one flight of stairs (10 ft), how much work would they do to climb up four flights of stairs (40 ft)?
4800 J
Work and displacement have a direct relationship, so quadrupling the displacement quadruples the work done.
300
Calculate the potential energy of a 12 kg mass sitting on a 2 m tall shelf.
PE = 240 J
PE=mgh=12(10)(2)=240 J
300
At which point is the ball's potential energy at a maximum? At which point is it's kinetic energy at a maximum?
PE is maximum at A, KE is maximum at D.
300
Power is the rate at which _____ is done.
Work
300
What year were both Mr. Crawford and the Nintendo 64 born?
1996
400
A 5000 N sack is placed on a donkey's back and the donkey carries it 2 kilometers across flat ground. How much work did the donkey do?
None! The force and the displacement are perpendicular.
400
Calculate the kinetic energy of a 12 kg mass moving at 4 m/s.
KE = 96 J
KE=0.5mv^2=0.5(12)(4^2)=96 J
400
Fill in all of the missing blanks in the diagram below.
1: PE = 0 J, KE = 1500 J
2: KE = 1000 J, E = 1500 J
3: PE = 1500 J, E = 1500 J
400
Which student does more work? Who has more power as they climb the stairs?
Student 2 does more work; both students have the same power.
400
What metro-Atlanta landmark featuring the largest granite carving in the world has Mr. Crawford been to the top of over 100 times?
Stone Mountain
500
A 10 kg bowling ball has a kinetic energy of 1100 J. How fast is the bowling ball moving?
14.8 m/s
KE=0.5mv^2 --> 1100=0.5(10)v^2
v^2=1100/5 --> v = sqrt(220) = 14.8 m/s
500
A rusty old toy car starts at the top of a 1.5 meter hill on a track. When the car is released, it only travels 1 meter up the hill on the other side, which means energy was not conserved. Why did this happen?
The car must have experienced a frictional force, which makes this an open system. The frictional force does negative work on the car, taking energy away from it and turning it into thermal energy.
500
A 20 kg box of books is lifted up on a 2 meter tall shelf in 4 seconds. How much power does the person have as they lift the box?
100 Watts
Fw = mg = 20*10 = 200 N
W = Fd = 200*2 = 400 J
P=W/t=400/4=100 W
500
Approximately how many miles has Mr. Crawford backpacked in his life? (Nearest answer wins)
About 2700 miles