10.3- POWER Flashcards
By what means cane energy be transferred from one object to another? (2)
work done by force due to one object making other object move
heat transfer from hot object to cold object
heat transfer ca n be due to conduction/ convection or radiation
What do electricity, sound waves + EM radiation i.e. light or radio waves transfer?
transfer energy
What happens to power the more energy transferred per second?
the more energy transferred per second, greater the power of transfer process
What is power defined as?
rate of transfer of energy
What is the unit of power?
watt (W)
Equation for power? (with energy)
P = ΔE/Δt
Energy for power? (with work)
P = ΔW/Δt
Equation for your gain in potential energy when going up flight of steps?
gain of potential energy = your weight * total height gain
Equation for muscle power?
power = energy transferred/ time taken = weight * height gain / time taken
When a powered object moves at constant velocity at constant height, what are the resistive forces like?
resistive forces (e.g. friction, air resistance, drag) equal + opposite to motive force
What is work done bye engine transferred into?
internal energy of surroundings by resistive forces
What is the work done per second for a powered vehicle driven by a constant force F moving at speed v?
work done per second = force * distance moved per second
What happens to output force when a powered object gains speed?
when powered object gains speed, output force exceeds resistive forces on it
What does work done by engine increase about a vehicle?
increases KE of vehicle + enables vehicle to overcome resistive forces acting on it
What is the motive power of a vehicle equal to?
motive power = energy per second wasted due to resistive force + gain of KE per second
