# 3.5 Component 5 – Physics: Energy, forces and the structure of matter

Forces are pushes or pulls, and if a force causes an object to move then work is done and energy is transferred. Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed. A braking force will cause an energy transfer that makes a vehicle slow down and heats the brakes. The braking distance of a vehicle depends on many different things, such as the speed of the vehicle.

The energy resources available to use may be divided into renewable and non-renewable. Energy can also be released from atoms, which contain smaller particles such as neutrons and protons in the nucleus, because atoms can break down to emit particles or gamma rays.

## Energy, energy transfers and energy resources

Students should have knowledge and understanding of the following content.

Content Additional guidance and suggested TDAs Specification reference GCSE Combined Science: Trilogy Specification reference GCSE Combined Science: Synergy
Outcome 1

Describe, for common situations, the changes involved in the way energy is stored when a system changes. For example:

• an object projected upwards
• a moving object hitting an obstacle
• a vehicle slowing down
• bringing water to a boil in an electric kettle.

Students may be required to describe the intended energy changes and the main energy wastages that occur in a range of devices.

Energy storage is limited to kinetic, gravitational potential, thermal and elastic potential.

6.2.1.1

4.1.1.4, 4.7.1.9 and 4.7.2.3

Outcome 2

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

6.1.2.1

4.8.2.5

The idea of efficiency. Whenever there are energy transfers in a system only part of the energy is usefully transferred. The rest of the energy is dissipated so that it is stored in less useful ways. This energy is often described as being 'wasted'.

Unwanted energy transfers can be reduced in a number of ways, eg through lubrication and the use of thermal insulation.

Calculations of efficiency will not be required.

Examples of the application of the idea of efficiency could include domestic appliances and vehicles.

4.8.2.6

How the rate of cooling of a building is affected by the thickness and thermal conductivity of its walls.

The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.

Suggested activity for TDA Investigate factors that affect the rate of cooling of a container of water, eg surface area, initial temperature, types of insulation, colour of the container.

Suggested activity for TDA Investigate the thermal conductivity of different materials, eg which is better for a saucepan handle: wood or metal?

Students do not need to know the definition of thermal conductivity.

6.1.2.1

4.8.2.6

Outcome 3

Describe the main energy resources available for use on Earth. These include fossil fuels (coal, oil and gas), nuclear fuel, bio-fuel, wind, hydro-electricity, geothermal, the tides, the Sun, water waves.

Distinguish between energy resources that are renewable and energy resources that are non-renewable.

Descriptions of how electricity is generated in a power station are not required other than the idea that a turbine is used to turn a generator.

6.1.3

4.8.2.4

## Forces and work

Students should have knowledge and understanding of the following content.

Content Additional guidance and suggested TDAs Specification reference GCSE Combined Science: Trilogy Specification reference GCSE Combined Science: Synergy
Outcome 4

A force is a push or pull that acts on an object due to the interaction with another object. All forces between objects are either:

• contact forces – the objects are physically touching
• non-contact forces – the objects are physically separated.

Examples of contact forces include friction, air resistance, tension and normal contact force.

Examples of non-contact forces are gravitational force, electrostatic force and magnetic force.

6.5.1.2

4.6.1.1

Outcome 5

When a force causes an object to move through a distance, work is done on the object.

Calculations involving work are not required.

6.5.2

4.6.1.3

Work done against the frictional forces acting on an object causes a rise in the temperature of the object. Suggested activity for TDA Investigate how different surfaces affect the amount of friction on a moving block.

6.5.2

4.7.1.10

## Speed and stopping distances

Students should have knowledge and understanding of the following content.

Content Additional guidance and suggested TDAs Specification reference GCSE Combined Science: Trilogy Specification reference GCSE Combined Science: Synergy
Outcome 6

Speed is measured by the distance travelled in a certain time.

Units of speed include metres per second and kilometres per hour.

Simple calculations of average speed using the equation: speed = distance/time will be required.

Suggested activity for TDA Investigate how the speed of a trolley changes as it rolls down a slope.

6.5.4.1.2

4.7.1.1

Outcome 7

The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver's reaction time (thinking distance) and the distance it travels under the braking force (braking distance).

For a given braking force the greater the speed of the vehicle, the greater the stopping distance.

Students may find it helpful to refer to the Highway Code.

6.5.4.3.1

4.7.1.10

Outcome 8

Reaction times vary from person to person. Typical values range from 0.2 s to 0.9 s.

Knowledge and understanding of methods used to measure human reaction times.

Knowledge of how a driver's reaction time can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver's ability to react.

Students should be able to interpret and evaluate measurements from simple methods to measure the different reaction times of students.

Students should be able to evaluate the effect of various factors on thinking distance.

Suggested activity for TDA Investigate factors that affect human reaction time, eg tiredness, distraction, practise.

6.5.4.3.2

4.2.1.6

Outcome 9

The braking distance of a vehicle can be affected by adverse road and weather conditions, and poor condition of the vehicle.

Students should be able to analyse a given situation to identify how braking could be affected.

Adverse road conditions include wet or icy conditions. Poor condition of the vehicle is limited to the vehicle's brakes or tyres.

6.5.4.3.3

4.7.1.10

Students should have knowledge and understanding of the following content.

Content Additional guidance and suggested TDAs Specification reference GCSE Combined Science: Trilogy Specification reference GCSE Combined Science: Synergy
Outcome 10

Some atomic nuclei are unstable. The nucleus gives out ionising radiation. This is a random process called radioactive decay.

The nuclear radiation emitted may be:

• alpha particles
• beta particles
• gamma rays.

Properties of alpha particles, beta particles and gamma rays limited to their penetration through materials and their range in air.

Students will be expected to know some of the uses and dangers of the three types of radiation.

6.4.2.1

4.3.2.2