OCR GCSE Combined Science B (21st Century) Paper 7 November 2020 question paper

The diagram shows a rollercoaster ride.

A motor pulls the train to the top of the track, 50 m above the ground. The weight of the train is 9000 N.

Calculate the potential energy gained by the train as it moves from the ground to the top of the track.

Give your answer in standard form.

It takes 15 s for the train to travel to the top of the track.

Calculate the useful power output of the motor.

What is meant by the term power output when discussing the train motor used in the rollercoaster?

The power output of the motor is equivalent to the rate / time / voltage at which energy is

transferred electrically / mechanically / by heating from the elastic / chemical / kinetic

energy store of the motor to the potential energy store of the train and to the

atmospheric / chemical / thermal energy store of the surroundings.

Sarah is investigating two circuit components.

She changes the potential difference across each component and measures the current through each component.

The table shows her results for component A.

Complete the graph in Fig. 2.1 by plotting the remaining two points from the table.

Draw a line of best fit on the graph in Fig. 2.1.

Describe the relationship between current and potential difference for component A

Suggest what component A could be.

Calculate the resistance of component A when the potential difference across it is 2.0 V.

Use data from the graph in Fig. 2.1.

Use the equation: potential difference = current × resistance

Resistance =........

Describe what happens to the current as the potential difference changes for component B.

Suggest what component B can be used for in a circuit.

This sign is used to mark sources of ionising radiation.

Name two types of ionising radiation.

Describe how ionising radiation is a hazard to humans.

Carbon dioxide in the atmosphere absorbs infrared radiation from the Earth.

Complete the following sentences to describe what happens when molecules of carbon dioxide absorb infrared radiation.

Use words from the list.

Each word can be used once, more than once or not at all.

decreases density faster increases mass

slower temperature

When molecules of carbon dioxide absorb infrared radiation, their internal store of energy

........

They move........ and the........ of the carbon dioxide

increases. If the carbon dioxide is in a container with a constant volume the pressure

........

Amaya looks up the relative atomic mass and the density of some metals.

Amaya makes a prediction.

She plots a graph of density against relative atomic mass for three metals.

Predict the density of tin from Amaya’s graph.

Show your working on Amaya’s graph.

Relative atomic mass of tin = 119

Predicted density of tin =........ g / cm³

Amaya concludes from her graph that the density of metals increases as the relative atomic mass of the metals increases.

The table shows the relative atomic mass and the density for two other metals.

Does the data in the table increase or decrease your confidence in Amaya’s conclusion?

Explain your answer.

The image of the plane water waves does not show up very clearly on the paper.

Suggest how you could improve the quality of the image on the white paper (screen).

Describe how to use the ripple tank to accurately measure the wavelength of a plane water wave.

Alex wants to find out if the temperature of the water affects the wavelength of the plane water waves in the ripple tank.

Suggest how he could change the experiment in (a)(ii) to see if the temperature of the water affects the wavelength of the plane water waves.

Alex counts 27 plane water waves passing a point on the white paper (screen) in 12 seconds.

Calculate the frequency of the plane water waves.

Alex measures the wavelength of a plane water wave to be 2.4 cm.

Calculate the speed of the plane water waves.

Use your answer to (b)(i).

Use the equation: wave speed = frequency × wavelength

Give your answer in m / s.

Speed =........ m / s

Kai investigates series and parallel circuits.

Kai makes two different circuits, as shown in Fig. 6.1. He uses identical resistors, ammeters, voltmeters and batteries.

The resistance of all 4 resistors is the same: R_A = R_B = R_C = R_D

Complete the sentences below about the two circuits.

The current at W is equal to / higher / lower than the current at Y.

The potential difference measured by voltmeter X is equal to / higher / lower than the

potential difference measured by voltmeter Z.

Kai replaces resistor R_A with another resistor that has much smaller resistance.

Describe what happens to the current measured by ammeter W and the potential difference measured by voltmeter X.

Fig. 6.2 shows the circuit diagram for an LED torch.

The potential difference between points A and B is 1.5 V.

How much work is done moving 300 mC of charge from A to B ?

When an electrical appliance is used, energy is transferred from one energy store to another, so there is a change in stored energy.

The table shows the change in stored energy for different electrical appliances.

Explain how the power rating of the appliance, and the time used, affects the change in stored energy.

Use data from the table to support your answer.

Calculate the useful energy transferred to the cordless vacuum cleaner motor when it is used for 0.4 hours.

The efficiency of the cordless vacuum cleaner motor is 90%.

Use data from the table.

Useful energy transferred =........ W h

Draw a labelled Sankey diagram to show the energy transfers that take place when the cordless vacuum cleaner is used for 0.4 hours.

Use information from the table and your answer to (b)(i).

The energy store at the start is the 50 W h chemical energy store of the battery in the cordless vacuum cleaner.

In 1986 there was an explosion at the Chernobyl nuclear reactor.

Caesium-137 is one of the largest sources of radioactivity left over from the explosion.

Caesium-137 has a half-life of 30 years.

Calculate the fraction of the radioactive emission from Caesium-137 that will still be present in 2076.

The first international reports of the explosion were made when measuring instruments in Sweden detected high radiation levels in the air.

Since the explosion at Chernobyl, scientists in many countries have shared their research on radiation levels and its effects.

Give two reasons why these scientists should communicate their work to the public, politicians and other scientists.

Geostationary satellites are used for communications and television broadcasting.

They travel in a circular orbit around Earth with a constant speed of 3 km / s.

Explain how a geostationary satellite can have constant speed but changing velocity.

A planet such as Earth has a large inertial mass.

Explain what is meant by inertial mass.

* This is a statement of Newton’s First Law:

When there is no resultant force on a stationary object it does not move. When there is no resultant force on a moving object it continues to move with constant velocity.

This equation represents Newton’s Second Law:

A space probe is travelling through space to a distant star. It is travelling through a vacuum and is not affected by any other objects. The space probe is on course to crash into the star.

Explain the motion of the space probe as it travels towards the star, and why it then crashes into the star.

You should apply Newton’s first law and Newton’s second law in your answer.

Jack puts 560 g of milk in a pan and heats it, taking care not to let it boil by using a thermometer. Energy is transferred from the pan to the milk.

Describe the effect on the milk.

Use ideas about energy stores in your answer.

Nina heats 560 g of water, using the same method that Jack uses for heating the milk.

Why does the temperature of the milk increase more quickly than the temperature of the water?

Nina heats the 560 g of water until it is boiling.

Calculate the energy needed to turn all the water to steam once it is boiling.

Specific latent heat of water = 2.23 × 10⁶ J kg^–1

Give your answer to 3 significant figures.

The time taken for all the water to turn to steam is 7 minutes.

Calculate the power of the heater used.

Use the equation: energy transferred = power × time

Beth investigates forces and magnetic fields.

State Newton’s third law.

When Beth sets the current in the wire to 5.6 A there is a force of 0.072 N on the wire. The wire has a length of 0.45 m.

Calculate the magnetic flux density.

Use the Data Sheet.

Give your answer in standard form and to 2 significant figures.