P3e: Energy on the move

Question 1

KE equation

Answer 1

KE (J) = 1/2 * mass (kg) * speed^2 (m/s)2

KE = 0.5mv^2

Question 2

Why is there a squared relationship between braking distance and speed?(4)

Answer 2

when a car stops, its kinetic energy changes into heat in the breaks, tyres and road
-shown by the formula: work done by brakes = loss in kinetic energy

loss in kinetic energy = braking force x braking distance

since the braking force cannot be increased, if the speed of the car doubles the kinetic energy that needs to be lost quadruples, so the braking distance quadruples to convert the extra kinetic energy

Question 3

Advantages of battery powered cars (2)

Answer 3

no combustion so no emissions/pollution at point of use unlike fossil fuels

quieter car

Question 4

Disadvantages of battery powered cars (4)

Answer 4

must be recharged using electricity produced from burning fossil fuels at power stations, pollution

batteries expensive to replace/car expensive initially to produce and make

pollution produced in their production

limited speed/performance/range

Question 5

Explain why electrically powered cars do not pollute at the point of use whereas fossil fuel cars do

Answer 5

electrically powered cars do not use combustion at the point of use, but fossil fuel cars do

Question 6

How may battery powered cars still produce pollution(3)

Answer 6

need to have the battery recharged

• this uses electricity produced from a power station
• power stations cause pollution.

Question 7

Explain the effect of bio-fuelled and solar powered vehicles on pollution(3)

Answer 7

reduce pollution at the point of use

produce pollution in their production

may lead to an overall reduction in CO2 emissions

Question 8

Why may we have to rely on bio-fuelled and solar powered vehicles in the future?

Answer 8

fossil fuels are non-renewable and will run out; bio-fuels and solar power are renewable

Question 9

Factors affecting fuel consumption (5)

Answer 9

amount of energy required to increase its kinetic energy(increased by mass and speed)

driving styles - excessive acceleration and deceleration, frequent breaking, speed changes - all increases fuel used

amount of energy required for it to do work against friction(reduced by more streamlined)

road conditions(rough surface, wet, icy) - increases frequency of braking and increases fuel used

speed