Energy on the move

Question 1

Relationship between braking distance and speed?

Answer 1

The braking distance of a car increases with increasing speed, but not proportionally.

Question 2

Kinetic energy

Answer 2

kinetic energy = ½mv²

• m = mass in kg
• v = velocity in m/s

Question 3

What happens when a car stops?

Answer 3

Its kinetic energy changes into heat in the brakes, tyre and road.

Question 4

Loss of kinetic energy

Answer 4

work done by brakes = loss of kinetic energy

Question 5

What forumula shows the change in kinetic energy?

Answer 5

Braking force x braking distance = loss in kinetic energy

Question 6

What happens when the speed of the car doubles?

Answer 6

• The kinetic energy and the braking distance quadruple.
• This is why there are speed limits and penalties for drivers who exceed the them.

Question 7

What is fuel consumption data based on?

Answer 7

Fuel consumption data is based on ideal road conditions for a car driven at a steady speed in urban and non-urban conditions.

Question 8

Factors that affect the fuel consumption of a car are:

Answer 8

• The amount of energy required to increase its kinetic energy.
• The amount of energy required for it do work against friction.
• Its speed.
• How it is driven, such as excessive acceleration and deacceleration, constant breaking and speed changes.
• Road conditions, such as a rough surface

Question 9

How are electric cars driven?

Answer 9

Electric cars are battery driven or solar-powered.

Question 10

Disadvantages of electric cars

Answer 10

• The battery takes up a lot of room.
• They have limited range before recharging.
• They are expensive to buy but the cost of recharging is low
• Solar-powered cars rely on the Sun shining and need backup batteries.

Question 11

Electric Cars and Pollution

Answer 11

• Battery-driven cars do not pollute the local environment, but their batteries need to be recharged.
• Recharging uses electricity from a power station. Power stations pollute the local atmosphere and cause acid rain.
• Solar-powered cars do not produce any carbon dioxide emissions.

Question 12

What do exhaust fumes do?

Answer 12

• Exhaust fumes from petrol-fuelled and diesel-fuelled cars cause serious pollution in towns and cities.
• Biofuels may reduce carbon dioxide emissions but this is not certain because deforestation leads to an increase in carbon dioxide levels.