Work
Conservation of Energy
Area under the curve
Labs
Power
100
A body builder holds a 100kg set of barbells at rest above her head for 30 seconds. How much work did the bodybuilder to on the barbells for the 30 seconds?
Zero
100
A mass is dropped from a height of 5m. How fast is it moving right before it strikes the ground?
10 m/s
100
What was the total amount of work done?
2500 J
100
You repeatedly drop a mass from various heights H and measure the speed when reaching the ground. What could you plot to get a straight line, and what would the slope represent?
Lots of answers
100
A 2kg cube sits without slipping on a 4m radius turntable that is rotating at a constant rate of 5Hz. What is the power put into the cube during one revolution?
Zero
200
A 3kg box slides down a 5m tall incline that makes an angle of 40 degrees with respect to the horizontal ground. How much work did the normal force do on the box?
0 Joules
200
A mass is shot with a speed of 7m/s up an inclined ramp that is angled 30 degrees from horizontal. How high vertically from the ground does the mass make it on the frictionless incline?
2.45 m
200
What was the total amount of work done?
30 J
200
You repeatedly give a mass initial speeds on a rough surface and measure how far it moves before skidding to a stop. What could you plot to get a straight line and what would the slope represent?
Lots of answers
200
It takes you a time T to lift a mass M from rest, to a height H at rest. What was the average power during the time T?
MGH/T
300
A 3kg box slides down a 5m tall incline that makes an angle of 40 degrees with respect to the horizontal ground. How much work did the force of gravity do on the box?
+150 J
300
With what speed will a spring of spring constant 300 N/m, compressed by an amount of 0.8m, be able to fire a 3kg mass from rest?
8 m/s
300
Assuming this 2.25 kg mass started from rest, how fast was it moving when it was displaced 0.6m?
4 m/s
300
You repeatedly start a mass M from rest against a spring of spring constant K which is compressed by different measured distances D. You measure the speeds S of the mass after the spring is released. What could you plot to get a straight line and what would the slope represent?
Lots of answers
300
A car of mass M speeds up from rest to a speed S in a time T. What was the average power output to achieve this?
(MS^2)/2T
400
A 2kg box starts with a speed of 6m/s. What is the speed of the mass after it has slid over a 2.5 m long rough patch floor of kinetic friction coefficient 0.4?
4 m/s
400
A mass slides down a 3m tall frictionless ramp and then over a horizontal rough patch of kinetic friction coefficient 0.2. How far did the mass travel over the horizontal ground before stopping?
15 m
400
Assuming this 5.6kg mass started from rest, how fast is it moving after it was displaced 8m?
5 m/s
400
You repeatedly drop a mass from various heights H and measure the speeds S right before they hit the ground. If you plot S vs. H, what would the shape of the graph look like? Draw it on board.
Like square root
400
A 400W motor will take how long to lift a 20kg mass a distance of 5m vertically in the air?
2.5 seconds
500
A force of 20N is applied to a 1kg mass that was initially at rest and can move along a horizontal frictionless ground. The force is applied at an angle of 30 degrees from vertical. What is the speed of the mass after it moves 5m along the horizontal surface?
10 m/s
500
A mass is released from rest at the top of a ramp of height H and slides down the inclined surface which has a coefficient of kinetic friction of Z. The angle the ramp makes with horizontal is T. What is the speed of the mass (symbolically) when it reaches the bottom of the incline?
[2gH-2gHZcosT/sinT]^1/2
500
Assuming this 0.2 mass started with a speed of 2m/s, how fast is it moving after it was displaced 0.1m by this force?
3.74 m/s
500
You repeatedly release a mass M from rest against a spring of spring constant K that is compressed by various distances D and measure the speeds S after being released from rest. If you were to plot the distance compressed D vs. S, what would the graph look like? Draw it.
Straight line
500
A 300W motor runs for 4 minutes. How much energy did it output?
72,000 J