3.3 Work Energy And Power

Question 1

What is work done equivalent to?

Answer 1

Energy transferred

Question 2

What are the SI base units equivalent to the Joule?

Answer 2

kgm^2 s^-2

Question 3

How is work done calculated

Answer 3

W = F x cosΘ (distance moved x component of the force in the direction of motion)

Question 4

What is Θ in W = F x cosΘ?

Answer 4

The angle between the force and motion.

Question 5

What is energy?

Answer 5

The capacity of one object or system to do work (or cause a change) on another.

Question 6

What is represented by the area under a force- distance graph?

Answer 6

Work done

Question 7

What is the principle of conservation of energy?

Answer 7

The energy of a closed system always remains constant. Energy can never be created or destroyed, only transferred from one from to another

Question 8

What form of energy is due to the motion of a mass?

Answer 8

Kinetic energy

Question 9

What form of energy is due to the position of a mass in a gravitational field?

Answer 9

Gravitational potential energy

Question 10

What form of energy is due to the bonds between atoms in a substance?

Answer 10

chemical energy

Question 11

What form of energy is due to a reversible change in shape of an object?

Answer 11

Elastic potential energy

Question 12

What form of energy is due to the position of a charge in an electric field?

Answer 12

Electrical potential energy

Question 13

What form of energy is due to the forces between protons and neutrons in an atom?

Answer 13

Nuclear energy

Question 14

What form of energy is due to electromagnetic waves?

Answer 14

Radiant energy

Question 15

What form of energy is due to the mechanical wave motion of atoms?

Answer 15

Sound energy

Question 16

What form of energy is due to randomly distributed potential and kinetic energies of the atoms within a system?

Answer 16

Thermal energy

Question 17

What effect does friction have on the energy of a moving object?

Answer 17

Transfers kinetic energy primarily to thermal energy

Question 18

Describe the energy transformations for an object sliding downhill at constant speed.

Answer 18

Gravitational potential energy decreases at the same rate as work is done by friction.

Question 19

Describe the energy transformations for a vehicle travelling uphill at constant speed.

Answer 19

Work is being done by the driving force and this is equal to the gain in gravitational potential energy plus work done by friction

Question 20

Power

Answer 20

Power is the rate at which work is done P = W/t

Question 21

What is the derived unit of Power?

Answer 21

Watt (W)

Question 22

SI unit of watt

Answer 22

kgm^2s^−3

Question 23

What is the equation P = Fv used for?

Answer 23

The power developed by an object moving at constant speed against a constant resistive force

Question 24

How is % efficiency calculated?

Answer 24

(Useful output energy/total input energy) x 100