What Is Energy?
What two factors affect the amount of potential energy that an object has?
Weight and height determine an object's potential energy.
A baseball flying through the air has what kind of energy?
kinetic energy
Compare and contrast power and work.
Both power and work are measures of the transfer of energy. Work is a measure of the amount of energy transferred, while power is a measure of the rate of the transfer of energy.
How high must you lift a 25-newton book for it to have the same increase in potential energy as a 20-newton book that was lifted 0.5 m?
The increase in gravitational potential energy of the 20-newton book is 10 J (20 N • 0.5 m = 10 J). The 25-newton book must be lifted to a height of 0.4 m to have an increase in gravitational potential energy of 10 J (25 N • 0.4 m = 10 J).
An object of mass 1.5 kg rests on a shelf where it has a gravitational potential energy of 7 joules. An object of mass 4.5 kg is placed on the same shelf. What is the gravitational potential energy of this second object?
21 joules
If a large truck and a small car are moving at the same speed, which has the greater kinetic energy? Why?
A large truck has greater kinetic energy because its mass is greater.
How is kinetic energy calculated?
Kinetic energy = ½ x mass x velocity2
How is energy related to work?
Work is the transfer of energy from one object to another.
How is power related to energy?
Power is the rate at which energy is transferred from one object to another.
Object A has a gravitational potential energy of 24 joules when it rests on a shelf 5 m above the ground. Object B has a mass that is three times the mass of Object A. What would be the gravitational potential energy of object B when it rests on a shelf 10 m above the ground?
144 joules
A 2-kg block rests on a wall that is 3 m tall. What is the gravitational potential energy of the block? The force of gravity on Earth (g) is equal to 9.8 m/s2.
58.8 joules
An object has a gravitational potential energy of 24 joules when it rests on a shelf 3 m above the ground. What would be its gravitational potential energy when it is lowered to a shelf 1 m above the ground?
8 joules
Describe the energy of a bowling ball as it rolls toward and hits a bowling pin.
Answers may vary. As the ball rolls, it has some energy. In other words, it has the ability to do work and move the pin some distance. When it hits the bowling pin, it does work on the pin. During this process, some energy is transferred from the ball to the pin. After hitting the pin, the bowling ball has less energy than before, so it slows down.
What happens to the kinetic energy of an object, if its velocity is doubled?
If the velocity of an object is doubled, its kinetic energy is multiplied by four.
15 joules of work are done by forces other than gravity in taking an object from a position 3 m above the ground to a position 8 m above the ground. What is the change in the gravitational potential energy of the object?
It increases by 15 joules.