Mechanics, Work and Energy

Question 1

What is Work done?

Answer 1

When a force moves an object and energy is transferred.

Question 2

How do we calculate Work done?

Answer 2

Work done = Force x distance, Work = Fd

Question 3

What energy is transferred if a force of 2N moves a distance of 10m?

Answer 3

Work = Fd Work = 2N x 10m = 20J

Question 4

If Work lifts an object against gravity what energy is gained?

Answer 4

Potential Gravitational Energy E_P

Question 5

What do the letters of this formula, E_P = mgh

Answer 5

Gravitational Potential energy = mass x acceleration against gravity (10ms^-2) x height

Question 6

Calculate the change in E_P when a person lifts 5kgs from the floor to a shelve 2m high.

Answer 6

E_p = mgh E_p = 5 x 10 x 2 = 100J

Question 7

What is Kinetic Energy?

Answer 7

The energy of a moving object E_K

Question 8

If an object is lifted higher what energy increases?

Answer 8

Gravitational Potential Energy (E_P)

Question 9

How does energy move through a system?

Answer 9

Energy is transferred from object to object

Question 10

What is happening to energy as an object falls?

Answer 10

E_P, Potential Gravitational Energy is transferred to E_K, Kinetic Energy

Question 11

What energy is formed when the Kinetic energy of a moving car has the brakes applied?

Answer 11

E_K to Heat in the brakes and tyres

Question 12

What energies are formed when the Kinetic energy of a Wind turbine is transferred?

Answer 12

Electrical, heat and sound.

Question 13

What energy is formed when a Roller coaster wagon is pulled up a ramp?

Answer 13

Gravitational Potential, heat and sound

Question 14

The amount of kinetic energy of an object relates to which to factors?

Answer 14

Mass (m) and speed (v)

Question 15

What is the calculation for E_K, Kinetic Energy?

Answer 15

E_K = ½mv²

Question 16

What happens to E_K if the speed is doubled?

Answer 16

4 x E_K

Question 17

What happens to E_K if the speed is trebled?

Answer 17

9 x E_K

Question 18

Calculate the Kinetic energy of a car with a mass of 800kg traveling at a speed of 10ms^-1

Answer 18

E_K = ½mv² Ek = ½800 x 10²

E_K = 400 x 100 = 40000 J

Question 19

How much Work is needed to stop a 800kg car traveling at 10m/s and has 40000J of Kinetic energy?

Answer 19

Work = energy transferred = 40000J of heat to the brakes and tyres.

Question 20

An 800kg car is traveling at 10ms^-1 with 40000 J of energy when the brakes are applied. It stops in 8m. What is the average force excerted by the brakes?

Answer 20

Work = Fd Therefore F = Work / d

F = 40000J / 8m = 5000N

Question 21

When Work is applied against frictional forces which is the main energy transferred?

Answer 21

Heat

Question 22

Why do we always show the formula when making calculations?

Answer 22

Marks can be gained for the correct formula even if the answer is wrong.

Question 23

What unit is Force measured in?

Answer 23

Newtons, N

Question 24

What unit is used to measure distance?

Answer 24

metres, m

Question 25

What units is used for Work?

Answer 25

Joules, J

Question 26

Name the units of this formula E_K = ½mv²

Answer 26

E_K is Kinetic energy, m is mass, v is speed

Question 27

What is the formula to calculate Power?

Answer 27

P = E/t Power = Energy / time

Question 28

What is Power?

Answer 28

The rate of doing Work or how quickly energy is transferred

Question 29

A ball has a mass of 0.1kg is dropped from a height of 1.5m. Assuming all the E_P is turned into E_K. How could you calculate the speed a ball would be falling at the moment before it hits the ground?

Answer 29

First calculate E_P = mgh, then because all E_P will be converted to E_K just before it hits the ground use ½mv² to calculate v

Question 30

Energy in battery contains of what form of energy?

Answer 30

Chemical potential

Question 31

A ringing bell is an example of what form of energy/energies?

Answer 31

Kinetic and Sound

Question 32

Food is contains what form of energy?

Answer 32

Chemical potential

Question 33

A stretched rubber band contains what form or energy?

Answer 33

Elastic potential

Question 34

What energy transfers take place while a TV is on?

Answer 34

Electrical to heat, light and sound

Question 35

What energy transfer takes place in an iron

Answer 35

Electrical to heat

Question 36

Describe the energy transfers that happen as someone parachutes to earth?

Answer 36

E_P decreases as E_K until terminal velocity is reached.