P1+ Conservation of Energy Flashcards
Year 9 (22 cards)
What is energy transfer?
The conversion of one store of energy into another.
Name the different ways energy can be transferred.
Heating, waves, electric current, and mechanically (by forces).
List the different energy stores.
List the different energy stores.
What is the law of conservation of energy?
Energy cannot be created or destroyed; it can only be transferred or dissipated.
What is a closed system?
A system where no energy transfers in or out take place (no dissipation).
Define work done in terms of energy.
Work done is the energy transferred by a force.
Write the equation for work done.
Work done = Force × Distance
What are the units for work done, force, and distance?
Joules (J), Newtons (N), metres (m) respectively.
What is weight?
The force acting on an object due to gravity.
Write the formula for gravitational potential energy (GPE).
GPE = mass × gravitational field strength × height
What units are used for GPE, mass, gravitational field strength, and height?
GPE increases when moving up and decreases when moving down.
What is extension in a spring?
The amount a spring stretches or compresses in metres.
Write the formula for kinetic energy (KE).
KE = 0.5 × mass × speed²
What are the units for kinetic energy, mass, and speed?
Joules (J), kilograms (kg), metres per second (m/s).
Write the formula for elastic potential energy (EPE).
EPE = 0.5 × spring constant × extension²
What happens to wasted energy?
It dissipates into the surroundings as heat and becomes less useful.
Define efficiency.
Efficiency = Useful energy output ÷ Total energy input
Can efficiency be greater than 100%?
No, efficiency can never be more than 100%.
How can machines be made more efficient?
By reducing energy wasted through methods like lubrication to reduce friction.
Write the formula for power
Power = Energy transferred ÷ Time taken
What are the units of power, energy, and time?
Watts (W), Joules (J), seconds (s).
