Work
What is the formula for work and standard units for each term?
Work = force * displacement
work in joules
force in newtons
displacement in meters
What is the formula of kinetic energy and standard units for each term?
KE = (1/2)mv^2
KE in joules
m in kg
v in m/s
What is the formula for GPE and each terms' standard units?
GPE = mgh
GPE is in Joules
m is in kg
g is in m/s^2
h is in meters
What is the formula for energy efficiency?
e = (Useful Energy Output/Total Energy Input)*100
150 J
A 5 kg ball is thrown at 10m/s. What is the kinetic energy of this ball?
250 J
A 0.1kg balloon has is floating at 45m in the air. How much GPE does it have?
45 J (using g = 10)
44.1 J (using g = 9.8)
mass and height of the object
How much work have you don after pushing on a wall with 100N of force for 20 seconds, but it does not budge?
0 J
A 1000 kg car has 12500 J of kinetic energy. What speed is it traveling at?
5m/s
A car is sitting on top of a 20m hill with 10000 J of GPE. How heavy is this car?
50 kg
Is 100% energy efficiency possible? Why?
No you will always lose some energy usually because of friction.
How much work is done by a 5 kg ball falling for 10 seconds at a speed of 20m/s?
10000 J
If the speed of an object doubles how much does the kinetic energy change by?
4 times
A 20 kg cart on a roller coaster, first drops you 10 meters then you rise 4 meters before dropping another 10 meters. How much more GPE do you have at the beginning as compared to the end of the roller coaster?
3200 J (using g = 10)
3136 J (using g = 9.8)
A ball starts on a 100m hill with 6000 J of potential energy and rolls down to the bottom in 10 seconds. If there is no friction, how much kinetic energy does it have at the bottom of the hill?
6000 J
You push a box with 20N of force and then let go. The box travels 10m while you are pushing and then continues to move 5m before stopping due to friction. How much work did you do on the box?
200 J
Two cars are traveling down a highway. Car A is 9 times heavier than Car B, but Car B is going 3 times faster than Car A. Which car has more kinetic energy?
Neither they have the same
The moon has gravity that is 1/6th as strong as Earth. How much less GPE does an object at 5m above the moon have as compared to 5m above Earth?
The GPE on the moon is 1/6th the GPE on Earth
What would a plot of KE vs v^2 look like? Use words from class to describe it.
It would look like a upwards linear line.