Kinetic Energy
Define kinetic energy.
Kinetic energy is the energy an object possesses due to its motion.
Define potential energy.
Potential energy is stored energy that can be released or transferred.
Calculate the gravitational potential energy of a 1 kg object raised 1 m above the ground.
E=mgh
g = 9.8
9.8j
Define energy transfer.
Energy transfer occurs when energy moves from one object or location to another.
Name the three methods of heat transfer.
Convection
Conduction
Radiation
What type of kinetic energy is associated with moving charges?
Electrical
dentify the type of potential energy possessed by a book on a high shelf.
Grav potential
A machine receives 100 J of energy and produces 80 J of useful output energy. Calculate its efficiency.
80%
Define energy transformation.
Energy transformation occurs when energy changes from one form to another.
Which method of heat transfer occurs when a metal spoon becomes hot in a pot of soup?
Conduction
Identify two types of kinetic energy involved in a television operating.
Light
Sound
Electrical
Identify the energy stored in a bow when it is pulled back before an arrow is released.
eleastic
A device receives 1000 J of energy and produces 250 J of useful output energy. Calculate its efficiency.
25%
Explain why energy is not destroyed when a machine becomes less efficient.
Energy is conserved. Some input energy is transferred into less useful forms, such as thermal energy and sound energy, rather than the intended useful output.
Explain why metals are generally good conductors of heat.
Metals contain particles and mobile electrons that transfer energy efficiently through the material.
Identify the kinetic energy types involved in a ringing bell.
Mechanical & sound
Explain why a full tank of petrol contains chemical potential energy.
Energy released when burnt
A 2500 g object is raised 8 m. Calculate its gravitational potential energy.
convert to kg (2.5 kg)
196J
Identify the useful and wasted energy outputs of an electric fan.
Useful = mechanical
wasted = sound
Explain why radiation can transfer heat through space but conduction cannot.
Conduction requires particles or material to transfer energy through contact. Radiation uses electromagnetic waves and does not require a medium.
A student claims that sound is not a form of energy because it cannot be seen. Explain why this claim is incorrect.
Sound is vibrating particles, hence move
A student places two identical books at different heights. Which book has more gravitational potential energy? Explain.
higher
more up more energy
A 15 kg object is lifted 12 m. Calculate its gravitational potential energy. A machine then transfers 2000 J of input energy and produces 1500 J of useful output energy. Calculate the machine's efficiency.
Part A – Gravitational potential energy:
E=15x9.8x12
=1764J
Part B – Efficiency:
Efficiency1500/2000 x 100
75%
A hydroelectric power station uses moving water to generate electricity. Construct an energy pathway.
Label the transfer & transformations
Gravitational potential energy → kinetic energy of moving water → kinetic energy of turbine → electrical energy.
A room is heated by a radiator. Describe how convection can help warm the room.
Air near the radiator heats up, expands and rises. Cooler air sinks and is heated. This creates a convection current that circulates warm air around the room.