Chapter 7 Flashcards
Which requires more work: lifting a 50-kg sack a vertical distance of 2 m or lifting a 25-kg sack a vertical distance of 4 m?
Both take the same 1000 J.
A car is raised a certain distance in a service-station lift, thus giving it potential energy relative to the floor. If it were raised twice as high, how much more potential energy would it have?
It would have twice as much potential energy.
Two cars are raised to the same elevation on service-station lifts. If one car is twice as massive as the other, compare their gains of potential energy.
The car with twice the mass has twice the gain of potential energy.
Compared with a car moving at some original speed, how much work must the brakes of a car supply to stop a car that is moving twice as fast? How will the stopping distances compare?
It takes four times the work and four times the stopping distance.
An apple hanging from a limb has potential energy because of its height. If it falls, what becomes of this energy just before it hits the ground? When it hits the ground?
Immediately before hitting the ground the apple’s energy is kinetic energy; when it hits the ground, its energy becomes thermal energy.
If an input of 100 J in a pulley system increases the potential energy of a load by 60 J, what is the efficiency of the system?
60%
The work that is done when twice the load is lifted twice the distance is _______.
four times as much.
When one does twice the work in twice the time, the power expended is _______.
the same.
When you lift twice the load twice as high, in half the time, the increase in potential energy is _______.
four times.
When traveling twice as fast your kinetic energy is increased _______.
When traveling twice as fast your kinetic energy is increased _______.
Energy cannot be _______.
destroyed.
