Energy stores
Energy transfers
Formulas
Units
Grab bag
100

As an object falls, which energy store decreases?

gravitational potential

100
Old-fashioned cars run on petrol. Their engines are designed to transfer energy from which store to which store?

from chemical store (of petrol) to kinetic store (of car)

100

In formulas, what symbol do we use for speed?

v

100

What units do we use to measure power?

watts (W)

100

What is the gravitational field strength near the surface of Earth?

9.8 N/kg

200

The amount of energy in an object's kinetic store depends on two things: its speed and what else?

its mass

200

An incandescent light bulb wastes a lot of energy. How is that wasted energy transferred to the surroundings?

as heat

200

In formulas, what symbol do we use for specific heat capacity?

c

200

Electrical work is measured in what units?

joules (J)

200
In a machine with moving parts, some energy is usually wasted due to what force?

friction

300

Energy stored in the bonds between atoms is said to be in which energy store?

chemical store

300

Thermal radiation is carried by which type of electromagnetic waves?

infrared waves

300

What equation relates mass, weight and gravitational field strength?

weight = mass x gravitational field strength

300

What units do we use to measure weight?

newtons (N)

300

Which energy resource is non-renewable: hydroelectric, biofuel, nuclear, geothermal?

nuclear

400

An inflated balloon has a lot of energy in which store?

elastic potential

400

If a hair dryer is 80% efficient, how much energy must be put in to get out 60 J of useful energy?

75 J

400

If the speed of an object doubles, how does its kinetic energy change?

KE quadruples
400

What units do we use to measure a spring constant?

newtons per metre (N/m)

400

How much work is done by a wire that holds up a 250 g weight 3 cm above the floor?

0 J

500

When a falling object hits the ground and comes to rest, energy from its kinetic store is ultimately transferred into which store?

thermal store (of object and surroundings)

500

When energy dissipates, it usually ends up in which energy store?

thermal store of surroundings

500

It takes a crane 20 seconds to lift 100 kilograms of concrete to a height of 30 metres. What is its power?

1,470 W

500

How many kilojoules (kJ) are in a megajoule (MJ)?

1 000

500

What is the specific heat capacity of water at room temperature?

approximately 4 200 J/(kgC)

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