Work
In order for work to be done, what must be true of force and displacement
they must be parallel (in the same direction)
if an object is not moving it has _____ Kinetic Energy
0
Gravitational Potential energy is the energy due to ____
position (height)
When is mechanical energy conserved?
when there is no external force
The unit for power is the
Watt. (or Joule/second)
What are the two ways to calculate work?
Force x Distance
Change in energy
At what point in a pendulum's swing is Kinetic energy the smallest?
at the top
You do 80 J of work to lift an object. How much energy has it gained?
80J
if friction is negligible, what will be the kinetic energy of an arrow that is shot out of a bow that has 70 J of elastic energy?
70 J
If a job done two different ways requires the same amount of work, how is power affected?
depends on the time
a car slows down on a flat road. is work being done?
yes (because it's Kinetic energy decreases, work must have been done)
two balls with equal masses roll on the floor. Ball A rolls at 1 m/s, and ball B rolls at 2 m/s. How many times more Kinetic Energy does ball B have than ball A?
4
What are the units for a spring constant k?
N/m (or N/cm)
Friction converts kinetic energy to ___
Heat (thermal energy)
The distance an object is pushed doubles while the time it takes to do the work is cut in half, what happens to the power?
4 times greater
You give your car a 200 N push and move it 2 m. How much work did you do on the car?
400J
If the velocity of an object triples its Kinetic Energy will be _____ times greater
nine
How much energy does a spring have when it compressed by 2m if the spring constant k = 1 N/m?
2 J
A 1 Kg pendulum has a velocity of 4 m/s at its fastest point (at the bottom). What height will it reach if energy is conserved?
0.8 m
If the power an object has triples what must have happened to its speed?
it tripled
A car with constant velocity rolls 30 meters. How much work was done?
none (no change in energy)
If the mass of an object doubles and its speed is cut in half, how will its Kinetic Energy change?
it will be cut in half
if the length of a stretched spring is is cut in half, its elastic potential energy would be _________
1/4
A 5 Kg ball dropped off of 10 m cliff will be going how fast when it reaches the ground?
14.1 m/s
You dissipate 50 Watts of power in 10 seconds. How much work did you do?
5 Joules