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| Question | Answer |
| P3e - Energy on the move | . |
| Kinetic Energy | All moving objects have kinetic energy. The kinetic energy an object has depends on its: Mass and Speed. |
| Calculating KE | KE = ½ mv2 or KE = ½ × m × v2 KE = the kinetic energy in joules, J m = the mass in kilograms, kg v = the speed in metres per second, m/s |
| Continue... | Since kinetic energy is proportional to the speed squared, braking distances for vehicles are also proportional to the speed squared. You may have to rearrange the equation for kinetic energy. For example: m = (2 × KE) ÷ v2 v2 = (2 × KE) ÷ m |
| When a car stops, its kinetic energy changes into heat in the brakes, tyres and road. | Work done by brakes = loss in kinetic energy The change in kinetic energy can be shown in the formula: braking force x braking distance = loss in kinetic energy |
| Fuels | The main fuels used in road transport (petrol and diesel) come from crude oil, which is a fossil fuel. Crude oil is a non-renewable resource which will run out one day if we continue to use it. In addition, petrol and diesel cause pollution when they are used. For example, they produce: - Carbon dioxide, which is a greenhouse gas linked to global warming - Sulfur dioxide, which is a cause of acid rain Scientists and engineers are looking at alternative ways to power vehicles. |
| Other fuels | Solar cells convert light energy into electrical energy. The electricity can be used to drive an electric motor in a car. Bio-fuels are fuels produced from living things or their products. |
| Factors that affect fuel consumption of a car | - the amount of energy required to do work against friction - its speed - how it's driven (excessive acceleration/deceleration) -road conditions |
| Electric vehicles | Unlike cars powered by fossil fuels, electric cars do not produce any pollution while they are being driven. However, they have to be recharged using electricity generated at a power station. This means that electric cars cause pollution at the power station. |
| Fuel Consumption (continue) | The shape of a vehicle is very important. Vehicles can be streamlined to produce less air resistance when they move, which decreases their fuel consumption and increases their range. On the other hand, roof boxes on cars increase air resistance, as does driving with the windows open. Increased air resistance increases fuel consumption and decreases the range. |
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