Energy

Recall and use multiples and sub-multiples of units, including giga (G), mega (M), kilo (k), centi (c), milli (m), micro (μ) and nano (n)

Prefixes scale units by powers of 10

Define weight, recall and use the equation

W = mg

Describe how weight is measured

Weight is directly measured using a calibrated spring balance or newtonmeter, which stretches dynamically based on the gravitational force acting on the object.

Describe the relationship between the weight of a body and the gravitational field strength

The weight of an object is directly proportional to the local gravitational field strength of the planet or body it is resting on.

Explain, using springs and other elastic objects, that stretching, bending or compressing an object requires more than one force

To alter the shape of a structural object permanently or temporarily, you must apply at least two opposing forces, otherwise the object will simply accelerate linearly in one direction instead of deforming.

Describe the difference between elastic and inelastic distortion

Elastic distortion allows an object to completely return to its original shape once the driving forces are removed, whereas inelastic distortion causes permanent change.

Recall and use the equation for linear elastic distortion including calculating the spring constant

F = kx

Use the equation to calculate the work done in stretching a spring

E = 0.5 * k * x^2

Describe the difference between linear and non-linear relationships between force and extension

A linear relationship displays a straight line on a graph where extension increases proportionally with force, whereas a non-linear relationship curves as the object deforms unevenly.

Describe the core practical setup to investigate the extension and work done when applying forces to a spring

Clamp a spring vertically next to a ruler, measure its initial length, systematically add mass hangers, record the new extension for each load, and plot a force-extension graph.

Recall and use the density equation

Density equals mass divided by volume (rho = m / V), where density is measured in kg/m^3 or g/cm^3.

Describe the core practical method to determine the density of an irregular solid object

Measure the mass of the solid using a digital balance, submerge it fully inside a displacement Eureka can filled with water, collect the overflow in a measuring cylinder to find its precise volume, and calculate density using mass divided by volume.

Describe the core practical method to determine the density of a liquid

Place an empty measuring cylinder on a balance, reset the scale to zero, pour a set volume of liquid inside, record the liquid volume, note the mass reading, and calculate density using mass divided by volume.

Explain the differences in density between the different states of matter in terms of the arrangements of the atoms or molecules

Solids are dense because tightly packed particles are locked closely in a fixed structure; liquids have slightly lower densities with close but fluid particles; gases have very low densities because their particles are widely separated with vast empty space between them.

Explain what is meant by conservation of energy

Energy cannot be created or destroyed, only transferred from one store to another, meaning the total energy of a closed system always remains completely constant.

Analyse the energy changes involved when an object is projected upwards or up a slope

The object's kinetic energy store decreases as it moves upward, while its gravitational potential energy store increases proportionally.

Analyse the energy changes involved when a moving object hits an obstacle

The kinetic energy store of the moving object decreases rapidly, transferring energy into the thermal store of the obstacle and surroundings, and into the environment via sound waves.

Analyse the energy changes involved when a vehicle slows down

The kinetic energy store of the vehicle decreases as friction in the brakes transfers energy directly into the thermal store of the brake discs and the surrounding air.

Analyse the energy changes involved when bringing water to a boil in an electric kettle

Electrical energy from the mains supply transfers energy into the thermal store of the heating element, which then transfers heat into the thermal store of the water.

Explain that mechanical processes become wasteful when they cause a rise in temperature so dissipating energy in heating the surroundings

Friction between moving parts causes mechanical systems to heat up, transferring energy into less useful thermal stores in the surroundings.

Explain ways of reducing unwanted energy transfer including through lubrication and thermal insulation

Lubricants reduce friction between moving parts to prevent thermal dissipation, while thermal insulation uses materials with low thermal conductivity to slow down heat loss.

Describe the effects of the thickness and thermal conductivity of the walls of a building on its rate of cooling qualitatively

Thick walls made of materials with low thermal conductivity reduce the rate of heat loss, keeping the building warm for longer.

Describe how to measure the work done by a force and understand its relationship to energy

Work done is a measure of mechanical energy transfer, where work done in joules is exactly equal to the energy transferred into or out of a system.

Recall and use the equation for work done

Work done = Force x distance moved in the direction of the force (W = Fd), where work is in joules (J), force is in newtons (N), and distance is in meters (m).

Recall and use the equation to calculate the change in gravitational PE when an object is raised above the ground

Delta GPE = m * g * Delta h, where mass is in kg, gravitational field strength is in N/kg, and change in height is in meters.

Recall and use the equation to calculate the amounts of energy associated with a moving object

Kinetic Energy = 0.5 * m * v^2, where mass is in kg and velocity is in m/s.

Recall and use the equation for efficiency

Efficiency = useful energy transferred by the device / total energy supplied to the device.

Explain how efficiency can be increased

Efficiency can be increased by reducing friction using lubricants, reducing resistance in electrical wires, or adding insulation to minimize unwanted thermal transfers.

Define power and recall its basic unit

Power is the rate at which energy is transferred or work is done over time, and it is measured in watts (W), where one watt is equal to one joule per second (J/s).

Recall and use the power equation relating energy and time

Power = energy transferred / time taken (P = E / t), which is equivalent to work done divided by time taken (P = W / t).

Explain the condition required for a body to remain at a constant temperature

To maintain a steady temperature, an object must radiate thermal energy out into its environment at the exact same average power rating that it absorbs radiation from its surroundings.

Explain what happens to a body if the average power it radiates is less or more than the average power it absorbs

If it radiates less power than it absorbs, its internal thermal store increases and its temperature rises; if it radiates more power than it absorbs, its thermal store decreases and its temperature drops.

Describe the core practical setup to investigate how the nature of a surface affects the amount of thermal energy radiated or absorbed

Fill a Leslie cube containing different surface faces (shiny metallic, dull matt black, white) with boiling water, and use an infrared detector or a thermometer placed at a fixed distance to measure the radiation emitted from each side.