OCR GCSE Combined Science A (Gateway) Physics Paper 12 Higher November 2020 question paper J250/12

Brakes are used to decelerate a car safely in order to reduce the risk of injuries to the passengers.

Which row in the table is correct when the brakes are used safely?

Electromagnetic waves have many uses.

Which row in the table is correct?

What is the typical value for human reaction time?

A 0.01 s

B 0.2 s

C 0.7 s

D 1.0 s

A ball is thrown vertically into the air.

Energy is transferred from a chemical store in the girl.

Which store is the useful energy transferred to?

A A chemical store only.

B A gravitational store only.

C A gravitational store and a chemical store only.

D A thermal store and a chemical store only.

A radioactive isotope emits only gamma rays.

A teacher places different materials in front of the isotope. She measures the reading on a Geiger-Muller tube connected to a counter.

Which row in the table shows the correct reading on the counter?

How can the efficiency of an energy transfer be increased?

A Decrease the total energy input.

B Decrease the wasted energy.

C Increase the total energy input.

D Increase the wasted energy.

A 1500 W heater is used for 1.5 hours.

What is the energy transferred in kWh?

Use the equation: energy transferred = power × time

A 2.25 kWh

B 135 kWh

C 2250 kWh

D 135 000 kWh

In glass, violet light refracts more than red light as it passes from air into glass.

Which statement explains why?

A Red light has a shorter wavelength.

B Red light slows down more than violet light.

C Violet light has a longer wavelength.

D Violet light slows down more than red light.

Thinking distance is directly proportional to speed.

The thinking distance at 30 mph is 9 m.

What is the thinking distance at 60 mph?

A 9 m

B 18 m

C 27 m

D 36 m

A student measures the temperature of a beaker of water as it cools down.

The graph in Fig. 11.1 shows how the temperature changes with time.

Calculate the rate of temperature change over the 5 minutes.

Rate of temperature change =........ °C / minute

Describe, in detail, how the temperature changes over the 5 minutes.

The beaker contains 0.2 kg of water.

The specific heat capacity of water is 4200 J / kg °C.

Calculate the change in thermal energy in the water after 5 minutes.

Give your answer to 1 significant figure.

Use an equation from the Data Sheet to help you.

Describe the change in energy stores as the water cools down.

The student is given some insulation. She wraps the insulation around the sides of the beaker and repeats the experiment.

Add another line to the graph in Fig. 11.1 to show how the temperature may change

when the beaker is wrapped with insulation.

State one thing the student can do to reduce the rate of cooling further.

Carbon-12 is a stable isotope. Carbon-14 is an unstable radioactive isotope.

Describe what is meant by the term isotope.

This is the equation for the radioactive decay of carbon-14:

Which type of radiation is emitted by carbon-14?

Describe how the mass and charge of the nucleus changes when the carbon-14 decays.

Mass........

Charge........

Carbon-14 can be used to date ancient objects.

An ancient object is 17 100 years old. The half-life of carbon-14 is 5700 years.

For the ancient object, what is the ratio of the original amount of carbon-14 to the amount of carbon-14 left?

This question is about sound, light and water waves.

State one difference between sound waves and light waves.

In Fig. 13.1, a student makes waves in a tray of water. He places a cork at position A.

Fig. 13.2 shows a free-body force diagram for the cork.

At position A in Fig. 13.1, the cork starts to move up.

Use the free-body force diagram to explain why.

Explain how this experiment shows that the wave travels but not the water.

A teacher uses a signal generator to produce a sound wave.

Fig. 13.3 shows the sound wave on the oscilloscope screen.

1 cm represents 0.005 s on the horizontal scale.

Calculate the period of the sound wave.

Calculate the frequency of the sound wave.

Fig. 13.4 shows the experiment a teacher does to measure the speed of sound.

She uses two microphones and a speaker.

• The speaker is connected to a signal generator.

• The speaker emits sound with a frequency of 1200 Hz.

• Microphone 2 is moved 0.29 m to the right of microphone 1.

• The traces on the oscilloscope screen are one wavelength apart.

Calculate the wave speed of sound.

Wave speed =........ m / s

Suggest how this experiment can be improved.

The speed of sound can also be calculated using echoes and a large wall.

Explain how.

This question is about the way electricity is used in the home.

The national grid transfers electrical power from power stations.

The table shows information for different types of power line.

The resistance of each power line is 3 .

Calculate the current in power line 3.

Use the equation: power = current² × resistance

Explain how power loss is reduced in the national grid.

Use the values for power line 1 and power line 2 to help you.

In Fig. 14.1, an electrician wires an electrical socket next to a sink.

The switch on the socket is open. Explain why this situation is dangerous if water enters the socket.

Write about the live wire and earth wire in your answer.

15* A turbine contains a rotating blade.

Fig. 15.1 is a diagram of a wind turbine and Fig. 15.2 is a diagram of a water (tidal) turbine.

A volume of air (wind) or water (tidal) flows through the turbine every second.

Some of the kinetic energy of the air or water is transferred.

This table gives information about wind and tidal turbines:

Compare the advantages and disadvantages of using each type of turbine.

Use kinetic energy calculations to support your answer.