Work
In order for work to be done, what must be true of force and displacement
they must be parrallel (same or opposite directions)
Potential energy is the energy due to ____
position / height above Earth's surface
When is mechanical energy conserved?
when there is no friction
The unit for power is called the
Watt or J/s.
If the sign of work is positive, this means that .....
force and displacement are in same directions. Example: pushing a box to the right and it moves to the right
The sign of kinetic enrgy is _rarely/sometimes/always/never__ positive
always
The work done lifting an object is _(greater than, equal to, or less than)____ its change in potential energy
equal to
What is the ability to do work?
Energy
Job A exerted 100 J of work in 10 seconds.
Job B exerted 100 J of work in 100 seconds.
Which Job used the most power?
Job A
Is work being done with lowering a cup to the table?
yes
Ball A has double the mass of ball B. How much KE does Ball A have compared to ball B?
twice as much
What are the units for Potential Energy?
Joules
Friction converts kinetic energy to ___
Heat
The distance an object is pushed remains the same while the time it takes to do the work is cut in half, what happens to the power?
twice as great
If the velocity of an object doubles, then its KE will be
quadrupled (4x)
PE + KE =
Total Mechanical Energy
if friction is negligible, the what will be the kinetic energy of an arrow that is shot out of a bow that has a potential energy of 70 J
70 J
The rate at which work is done on an object.
Power
If speed is constant during the motion, will it affect how much work is done
no
If friction is the only force acting on an object, what will happen to the object's KE?
decrease
If the height of the object doubles, then the PE will
also double
Energy is changed from one form to another with no net loss or gain is ________ (T or F)
Always true
The Horsepower unit is a measurement of ______.
Power