Simplified P3 - Work and Power, Energy on the move, Crumple Zones

Question 1

When is work done?

Answer 1

Work is done when a force moves an object in the direction in which the force acts.

Question 2

What is weight?

Answer 2

Weight is a measure of gravitational attraction on a body acting towards the centre of the Earth.
1 kg mass has a weight of 10n on earth.

Question 3

What is power?

Answer 3

Power is the rate at which work is done.

Question 4

What does the power rating of a car depend on?

Answer 4

The power rating of a car depends on its engine size, more powerful cars have greater fuel consumption.
- Some cars are more powerful than others. They travel faster and cover the same distance in a shorter time and require more fuel.

Question 5

What is an issue with high fuel consumption cars?

Answer 5

Fuel is expensive and cars with high fuel consumption are expensive to run.

Question 6

What is an issue with current fuels used today?

Answer 6

• Fuels pollute the environment
  
  • Cars exhaust gases, especially carbon dioxide, are carbon dioxide are harmful
  • Carbon dioxide is also a major source of greenhouse gas, which contributes to climate change.

Question 7

What is the correlation between braking distance and speed?

Answer 7

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

Question 8

What happens to kinetic energy when a car stops?

Answer 8

When a car stops its kinetic energy changes into heat in the brakes, tyres and road.

Question 9

What happens to the kinetic energy when the speed of a car doubles?

Answer 9

When the speed of a car doubles the kinetic energy and the braking distance quadruple.
- This is why there are speed limits, and penalties for drivers who exceed them.

Question 10

What is fuel consumption data based on?

Answer 10

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

Question 11

What factors affect the fuel consumption of a car?

Answer 11

The factors that affect the fuel consumption of a car are:

• The amount of energy required to increase it’s kinetic energy.
• The amount of energy required for it to do work against friction
• Its speed
• How it is driven, such as excessive acceleration and deceleration, constant braking and speed changes.
• road conditions, such as a rough surface.

Question 12

What are Electric cars?

Answer 12

Electric cars are cars that are battery driven or solar powered.

Question 13

What are the downsides to electric cars?

Answer 13

• Battery takes up a lot of room
• They have a 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 14

What are problems associated with exhaust fumes?

Answer 14

• Exhaust fumes from petrol fuelled and diesel fuelled cars cause serious pollution in towns and cities.

Question 15

How do battery driven cars indirectly contribute to global warming?

Answer 15

• Battery driven cars themselves 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.

Question 16

What is a positive of solar powered cars?

Answer 16

They do not produce any carbon dioxide emissions.

Question 17

What are issues with biofuels?

Answer 17

Biofuels may reduce carbon dioxide emissions, but this is not certain because deforestation leads to an increase in carbon dioxide levels.

Question 18

How are injuries reduced in a collision?

Answer 18

To reduce injuries in a collision, forces should be as small as possible.

Question 19

How can you reduce the force in a collision ( momentum ) ?

Answer 19

Spreading the momentum change over a longer time reduces the force.

Question 20

How can forces be reduced by reducing the acceleration?

Answer 20

• Increasing the stopping or collision time.

- Increasing stopping or collision distance

Question 21

What are some safety features modern cars have to absorb energy when a vehicle stops suddenly?

Answer 21

• Brakes that get hot
• Crumple zones that change shape to absorb force
• Seat belts that stretch
• Air bags that inflate and squash

Question 22

What are some safety features that modern cars have to absorb energy on impact?

Answer 22

• Crumple zones at the front and rear of the car absorb energy by changing shape or “crumpling”
• Seat belts that stretch a little so that some of the person’s kinetic energy is converted to elastic energy.
• Air bags absorb some of the person’s kinetic energy by squashing up around them.

Question 23

Why do some people not like wearing seatbelts?

Answer 23

• There is a risk of chest injury.
• They may be trapped in a fire
• Drivers may be encouraged to drive less carefully because they know they have protection from a seat belt.

Question 24

What is an advantage of real tests over computer simulations?

Answer 24

• Real tests provide more accurate data than computer simulations.

Question 25

What happens in ABS system?

Answer 25

• Wheel speed sensors send information to a computer about the rotational speed of the wheels
• The computer controls the pressure to the brakes, via a pump.
• This is to prevent the wheels locking up
• This increasing the braking force right before the wheels start to skid.

Question 26

What are some primary safety features of a car?

Answer 26

• Cruise control which stops drivers becoming tired on a long journey and pressing harder on the accelerator.
• Electric windows and paddle shift controls which allow the driver to concentrate on the road
• ABS brake lock systems to prevent brakes locking up.