Work Done And Power Flashcards

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1
Q

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

A
  • work is done on the object

- and energy is transferred

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2
Q

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

A

an external force needs to act on it

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3
Q

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

A
  • a source of energy

- like food, fuel or electricity

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4
Q

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

A

the energy is transferred mechanically from one store to another

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5
Q

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

A
  • no, they are both still work done

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

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6
Q

what is the equation for calculating work done

A
  • work done = force x distance

- E = F * d

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7
Q

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

A
  • work done is measured in joules (J)
  • force is measured in newtons (N)
  • distance is measured in meters (m)
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8
Q

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

A

1 joule of work

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9
Q

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

A
  • 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
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10
Q

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

A
  • 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
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11
Q

what is the equation for effiency

A

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

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12
Q

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

A
  • 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
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13
Q

what is power

A
  • 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
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14
Q

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

A
  • watts (W)

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

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15
Q

what is the formula for power

A
  • power = work done / time taken

- p = e/t

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16
Q

what should you remember when talking about power and defining it

A
  • 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
17
Q

what does a larger power of an object indicate

A

more work being done per second