energy exam questions Flashcards
it is unlikely that all of the electricity that the UK needs can be generated by solar power systems. explain why (2)
-low useful output of solar cells
-so a large area of land has to be converted to solar cells
-the number of hours of daylight in the UK are too low
when electric cars are not being driven, energy stored in their batteries could be used to meet sudden peaks in electricity demand. suggest how. (2)
-when cars are plugged in
-the energy from the car can be transferred back to the national grid
in a theme park, a light gate and a data logger can be used to determine the speed of each rider and sled. what two measurements are needed to determine the speed of a rider and sled? (2)
-length of sled
-time for sled to pass light gate
in a theme park, at the bottom of the slide all riders and their sleds have approximately the same speed. explain why (4)
-decrease in eP = increase in eK
-both masses cancel out on both sides of the equation
-the final speed only depends on height
-there will be some variation due to air resistance/ friction
An ice cube has a temperature of −15.0 °C
The total thermal energy needed to raise the temperature of this ice cube to 0.0 °C and
completely melt the ice cube is 5848 J
specific heat capacity of ice = 2100 J/kg °C
specific latent heat of fusion of ice = 334 000 J/kg
Calculate the mass of the ice cube.
E = m × 2100 × 15
E = m × 334 000
5848 = 31 500 m + 334 000 m
or
5848 = 365 500 m
m = 0.016 (kg)
an electric car has a range of 400km with fully charged battery. a disel car has range of 1220km with full tank. explain the different in time needed to complete a 500 km journey using the electric car compared to the diesel car. assume they both travel at the same speed (2)
- the electric car would take longer than diesel car
- as it would have to stop and recharge its battery to travel the last 100 km
coils of wire are underground to charge electric cars whilst they are driving. suggest 2 advantages of doing this rather than using the main electricity supply (2)
- the cars do not have to stop to recharge
- a smaller battery can be used in the car
when electric cars are not being driven, energy stored in them can meet sudden peaks in demand from the national grid. suggest how this can be done. (2)
- when the car is plugged in
- the energy from the car can be transferred back to the national grid
a light gate and data logger can be used to determine the speed of each rider and sled. what other 2 measurements are needed to determine the speed? (2)
length of sled
time for sled to pass through light gate
At the bottom of a roller-coaster slide, all riders and their sleds have approximately the same speed.
Explain why. (4)
- decrease in Ep = increase in Ek
- masses cancel on both sides of the equation
- final speed only depends on vertical height
- will be some variations will be due to air resistance and friction
Give two environmental advantages of using a gas-fired power station to generate
electricity compared with using a coal-fired power station. (2)
- less global warming
- less carbon dioxide released
The motor in the lawn mower can only be turned on when the person using it holds the
handle of the lawn mower with both hands.
Explain why. (2)
- both switches need to be closed
- to allow charge to flow
When the kettle was switched on the temperature of the water did not immediately start to
increase.
Suggest one reason why. (1)
the heating element of the kettle takes time to heat up
As the person moves down the zip wire her increase in kinetic energy is less than her
decrease in gravitational potential energy.
Explain why (2)
- work done against air resistance
- causes thermal energy to be transferred to surroundings
Different people have different speeds at the end of the zip wire.
Explain why. (2)
- different people have different surface areas
- so they would be affected by air resistance differently
