Physics Homework 26.1.25 Flashcards
[Energy 3]
Two torches each have an input power of 50W. Torch A has a useful output of 40W. Torch B has a useful output of 45W. State and explain which torch is more efficient.
Torch B; It outputs 90% of the input power in contrast to 80%.
Name the store of energy associated with batteries.
The chemical energy store.
In words, state the question that link efficiency, total input power and useful output power.
efficiency = useful output power / total input power.
State the calculation for establishing the extension of a spring given its final and initial length.
final length - initial length.
Name the transfer of energy associated with forces changing the shape of an object.
Mechanical transfer.
Name the transfer of energy associated with an object emitting sound or light.
Radiation transfer.
Describe the change in the elastic potential energy store as an object becomes more compressed.
It increases.
Describe the change in the gravitational potential energy store as the height of an object decreases.
It decreases.
Name the store of energy that the lubrication of moving parts will reduce energy transfers to.
The thermal energy store.
What are the units of efficiency?
There are no units.
State the standard units for power.
Watts - W
In words, state the equation that links efficiency, total input energy transfer and useful output energy transfer.
efficiency = useful output energy transfer / total input energy transfer
Two heaters each have a useful output power of 2000W. Heater A has an input power of 2500W. Heater B has an input power of 2600W. State and explain which heater is more efficient.
Heater A; The waste percentage is smaller.
State the law of the conservation of energy.
Energy cannot be created or destroyed, it can only be transferred between one store to another.
Name the transfer of energy associated with one object increasing the temperature of another.
Heating transfer.
State the standard units for work done.
Joules - J
Describe the change in the elastic potential energy store as the extension of an object decreases.
It decreases.
In terms of energy, define efficient.
Only a small percentage (or small fraction) of the input energy is wasted.
Describe the change in the kinetic energy store as the speed of an object decreases.
It decreases.
Name the energy store associated with fuels.
The chemical energy store.
