Work, energy and power Flashcards
Energy is…
the ability to perform any work.
When work is done…
energy is transferred.
Energy cannot be…
destroyed or created only changed to other forms.
Work is…
the energy transfer that takes place when a force causes an object to move.
Work is done only when…
there is a change in energy.
Work done=
force applied x distance moved in the direction of the force
1j =
1 Nm
Kinetic energy =
0.5mv2
Force-distance graph:
-the area is the work done
When there is no constant force applied:
(F/2)d - =average force
Work done is positive when…
it is done by force and negative when it is done on the force.
Work done by gas=
pressure x change in volume
The equation for gas is relevant when:
- there is a constant pressure
- change in gas volume
Gravitational potential energy is…
the energy of an object due to its position in a gravitational field.
ΔEp=
mass x g x Δh
E.p. is directly proportional to…
height.
Kinetic energy is…
the energy of an object due to its speed.
Ek =
0.5 x mass x v2
Resistive forces are…
the forces that act on the moving object in the opposite direction of the direction of movement.
Power is…
the rate at which work is done.
Power =
work done/time taken
Power is measured in…
Watts.
Motive power is…
the power outputted by a powered object.
Efficiency is…
the ratio of useful work done by a device, to total work done.
Sankey diagram:
- arrows that bend are dissipated energy
- straight arrow is useful energy
