Mechanics

Question 1

Work is done whenever…

Answer 1

Energy is transferred

Question 2

What is needed to move something?

Answer 2

• Usually you need a force to move something because you’re having to overcome another force.
  -The thing being moved has kinetic energy while its moving. - — The kinetic energy is transferred to another form of energy when the movement stops

Question 3

Define the word ‘work’

Answer 3

The word work in physics means the amount of energy transferred from one form to another when a force causes a movement of some sort

Question 4

What is the equation used to calculate the work done?

Answer 4

• Work done (W) = Force causing motion (F) * distance moved (s)
• W = Fs

Question 5

What is work done measured in?

Answer 5

Joules

Question 6

What is force measured in?

Answer 6

Newtons

Question 7

What is distance measured in?

Answer 7

Metres

Question 8

What are the key points to remember about the W=Fs equation?

Answer 8

1- Work is the energy that’s been changed from one form to another - it’s not necessarily the total energy. E.g. moving a book from a low shelf to a higher one will increases its gpe but it had some gpe to start with. Here the work done would be the increase in gpe, not the total gpe
2- The distance needs to be measured in metres
3 - The force F will be a fixed value in any calculations either because its constant or because its the average force
4 - The equation assumes that the direction of the force is the same as the direction of movement
5 - The equation gives you the definition of the joule,
‘One joule is the work done when a force of 1 newton moves an object through a distance of 1 metre’

Question 9

Which formula is used to calculate the work done when the direction of movement is different to the direction of the force?

Answer 9

W=FsCosθ

Question 10

In the formula W=FsCosθ what is θ?

Answer 10

θ is the angle between the direction of the force and the direction of motion

Question 11

When calculating work done where the direction of movement is different to the direction of the force which force should be used in the equation?

Answer 11

The force which is causing the motion

Question 12

What is the area under a force-distance graph equal to?

Answer 12

The work done

Question 13

How can work done be calculated from a force-distance graph?

Answer 13

By calculating the area under the graph

Question 14

If a force-distance graph is irregular shaped how can the area underneath it be calculated?

Answer 14

The graph can be split into shapes and the area of each individual shape can be calculated

Question 15

Define power

Answer 15

Power is the rate of doing work - it is the amount of energy transferred from one form to another per second

Question 16

What equation can be used to calculate power given work done and time?

Answer 16

Power = Change in energy (work done) / change in time
P = ΔW/Δt

Question 17

Define the watt

Answer 17

The watt is a rate of energy transfer equal to 1 joule per second

Question 18

What is the equation for calculating power given force and velocity?

Answer 18

Power = Force * Velocity
P=Fv

Question 19

Define the principle of conservation of energy

Answer 19

Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change

Question 20

What is the equation used to calculate efficiency?

Answer 20

Efficiency = Useful output power / Input power

Question 21

How can you get efficiency as a percentage?

Answer 21

You can multiply the efficiency by 100 to get it as a percentage

Question 22

What is kinetic energy?

Answer 22

Kinetic energy is the energy of anything moving

Question 23

What is the formula for calculating kinetic energy and what are each of the variables?

Answer 23

Ek = 1/2mv^2
- v is velocity
- m is mass

Question 24

What are the different types of potential energy?

Answer 24

Gravitational and elastic

Question 25

What is gravitational potential energy?

Answer 25

Gravitational potential energy is the energy something gains if you lift it up

Question 26

What is the formula for calculating gravitational potential energy and what are each of the variables?

Answer 26

ΔEp = mgΔh
- m is the mass of the object
- Δh is the height the object is lifted
- g is the gravitational field strength

Question 27

What is elastic strain energy? (elastic potential energy)

Answer 27

Elastic strain energy is the energy you get in say a stretched rubber band or spring

Question 28

What is the formula for calculating elastic strain energy and what are each of the variables?

Answer 28

E = 1/2kΔl^2
- Δl is the extension of the spring
- k is the spring constant