Chapter 7 Questions Flashcards
When is energy most evident?
when it is changing
cite an ecample in which a force is exerted on an object without doing work on the object
no work is done pushing on a stationary wall
exactly what is it that enables an object to do work
energy enables and object to do work
a car is raised a certain distance and therefore has PE relative to the floor. If it were raised twice as high, how much PE?
2 the PE because the distance is two times greater
when is the potential energy of something significant
when it changes, does work, or transforms to another form
how much work must the brakes of a car supply to stop a car that is moving 2x fast? how will the stopping distances compare
4 times as much work b/c of 4 times stopping distance
how does speed affect the friction b/w a road and a skidding tire
speed has a little or no effect on friction
if an apple falls, what becomes of this energy before it hits the ground? When it hits the ground?
its initial PE becomes KE, when it hits ground TE
What is recycled energy
employment of energy that otherwise would be wasted
the work done in pushing a TV set a distance of 2 m with and average force of 20 N is
40 J
the work you do when pushing a shopping cart twice as far while applying the same force is
twice as much
an object that has kinetic energy must be
moving
two identical golf carts move at different speeds. The faster cart has twice the speed and thereforce has
four time the kinetic energy
a ball rolling down an incline has its maximum PE at
the top
a ball rolling down an incline has its maximum KE at
the bottom
a 50-kg is lifted 2 meters from the ground. A 25-kg sack is lifted 4 meters at the same time. The work performed in raising the 50-kg sack is the same
50(2)= 100, 25(4)= 100, the same
relative to an intial height an object raised twice as high has a GPE
twice as much
when a drawn bow of PE 40 J is fired, the arrow will ideally have a KE of
40 J
