Work Done And Power

Question 1

what is the effect of a force moving an object through a distance

Answer 1

• work is done on the object

- and energy is transferred

Question 2

what is the number one rule when having to make something move

Answer 2

an external force needs to act on it

Question 3

what does the thing applying the force on the object ,that it is going to move, need in order to do so

Answer 3

• a source of energy

- like food, fuel or electricity

Question 4

how is energy transferred when a force does work to move an object

Answer 4

the energy is transferred mechanically from one store to another

Question 5

is there a difference between energy being transferred usefully or being wasted in terms of changing the work done and why

Answer 5

• no, they are both still work done

- because work done and energy transferred are one in the same

Question 6

what is the equation for calculating work done

Answer 6

• work done = force x distance

- E = F * d

Question 7

what are the units of measurement for work done, force and distance

Answer 7

• work done is measured in joules (J)
• force is measured in newtons (N)
• distance is measured in meters (m)

Question 8

how much work is done when a force of 1 newton causes an object to move 1 meter

Answer 8

1 joule of work

Question 9

how would you describe the energy transfer and work done of a tyre being lifted into the air

Answer 9

• work is being done against gravity
• the kinetic energy of whatever is lifting the tyre is being transferred tot he gravitational potential energy stores of the tyre

Question 10

what does a force doing work often cause (no matter how small) and what does this mean in terms of efficiency

Answer 10

• a rise in temperature
• as energy is dissipated to the thermal energy stores of the moving object and its surroundings
• meaning that the process is wasteful and the efficiency of the process is reduced

Question 11

what is the equation for effiency

Answer 11

efficiency = useful energy transferred by device / total energy supplied to device

Question 12

explain the energy transfers and work done from someone pushing a box along a rough surface

Answer 12

• work is being done against the frictional forces the box would experience from the rough surface
• this causes the transfer of chemical energy from the person pushing the box to the kinetic energy stores of the box as it moves
• but some energy is also being transferred to the thermal energy stores of the box
• this causes the overall temperature of the box to increase

Question 13

what is power

Answer 13

• the rate of energy transfer
• how much work is being done every second
• the measurement of how quickly energy is transferred
• pick any of em

Question 14

what is the unit of power and what is another way of writing it

Answer 14

• watts (W)

- you could also say that 1 W = 1 J/s

Question 15

what is the formula for power

Answer 15

• power = work done / time taken

- p = e/t

Question 16

what should you remember when talking about power and defining it

Answer 16

• work done and energy transferred are more or less t he same thing or will have the same numerical value
• so it is fine to take that power = energy transferred / time

Question 17

what does a larger power of an object indicate

Answer 17

more work being done per second