Gravity and weight

Very long trains can be pulled by more than one engine.

A train is made up of four engines pulling trucks filled with coal.

The coal in one truck has a mass of 75 000 kg.

gravitational field strength = 9.8 N/kg

Calculate the weight of the coal in one truck.

Use the equation:

weight = mass × gravitational field strength

One engine exerts a forward force of 850 000 N.

Calculate the work done by one engine when the train moves a distance of 80 m.

Use the equation:

work done = force × distance moved

Each of the four engines exerts a forward force of 850 000 N on the trucks.

Calculate the total forward force on the trucks.

The force exerted by the engines on the trucks is a contact force.

Which of the following is also a contact force?

Tick (✓) one box.

Which sketch graph represents the train moving at a constant speed?

Tick (✓) one box.

The train accelerates for 150 s.

The velocity of the train changes from 16 m/s to 25 m/s.

Calculate the acceleration of the train.

Use the equation:

A swimming pool is being filled with water.

Calculate the weight of the water in the swimming pool when the mass of the water is 25 000 kg.

gravitational field strength = 9.8 N/kg

Use the equation:

weight = mass × gravitational field strength

When the swimming pool is full, the weight of the water is 1 960 000 N.

The bottom of the swimming pool has an area of 49 m².

Calculate the pressure at the bottom of the swimming pool when it is full.

Use the equation:

Choose the unit from the box.

There is a force acting on the side of the swimming pool because of the water pressure.

Figure 11 shows the side of the swimming pool.

Which arrow shows the direction of the force acting on the side of the swimming pool?

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A child is swimming in the pool. The velocity of the child is 0.70 m/s.

The child then accelerates for 5.0 s, reaching a final velocity of 1.3 m/s.

Calculate the acceleration of the child.

Use the equation:

Figure 12 shows a diving board at the side of the swimming pool.

The original length of the spring is 0.84 m.

When the child stands on the diving board, the length of the spring decreases by 0.21 m.

Calculate the percentage change in the length of the spring.

Use the Physics Equations Sheet to answer questions 07.6 and 07.7.

Write down the equation which links extension (e), force applied to a spring (F) and spring constant (k).

The force applied to the spring by the weight of the child is 336 N.

The change in length of the spring is 0.21 m.

Calculate the spring constant of the spring.

The child steps off the diving board and falls into the swimming pool.

The initial velocity of the child is 0 m/s.

acceleration due to gravity = 9.8 m/s²

Calculate the final velocity when the child has fallen a distance of 0.95 m through the air.

Give your answer to 2 significant figures.

Use the Physics Equations Sheet.

A student carried out an investigation to determine the spring constant of a spring. Figure 1 shows the spring before and after a mass was hung from the end of the spring.

What is the extension of the spring in Figure 1 ? Tick (✓) one box.

Give one safety precaution the student should have taken during this investigation.

The student hung a mass of 0.050 kg from the spring. gravitational field strength = 9.8 N/kg Calculate the weight of the 0.050 kg mass. Use the equation: weight = mass × gravitational field strength

The weight of the mass applies a force to the spring. The student added more masses and recorded the extension of the spring. Which graph in Figure 2 shows the relationship between the force applied to the spring and the extension of the spring? Tick (✓) one box.

A force of 2.0 N was applied to a different spring. The extension of the spring was 0.080 m. Calculate the spring constant of the spring. Use the equation:

Figure 17 shows the Hubble Space Telescope orbiting the Earth.

What name is given to an object that orbits a planet? Tick (✓) one box.

The Earth exerts a gravitational force on the Hubble Space Telescope. Draw an arrow on Figure 17 to show the gravitational force.

Figure 18 shows how the distance travelled by the Hubble Space Telescope during its orbit changes with time.

The gradient of the line in Figure 18 gives the speed of the Hubble Space Telescope. Determine the speed of the Hubble Space Telescope. Give your answer in km/s.

The Hubble Space Telescope can detect the visible light spectra from distant galaxies. The visible light spectra from stars and galaxies include dark lines at specific wavelengths. Figure 19 shows the visible light spectra from the Sun and three galaxies.

Which galaxy is moving away from the Earth the fastest? Tick (✓) one box.

Which galaxy is the furthest away from the Earth? Tick (✓) one box.

New scientific observations indicate that many galaxies rotate too quickly for the known mass of the stars they contain. Why is it important that new scientific observations are peer reviewed? Tick (✓) one box.

Hailstones are small balls of ice. Hailstones form in clouds and fall to the ground.

Figure 3 shows different-sized hailstones.

Which force causes the hailstones to fall to the ground?

Tick (✓) one box.

As the hailstones begin to fall they accelerate.

Which force increases as the hailstones accelerate?

Tick (✓) one box.

After a short time hailstones fall at terminal velocity.

Which of the following statements is true at terminal velocity?

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A scientist investigated how the terminal velocity of hailstones varies with their diameter.

Figure 4 shows the results.

Estimate the terminal velocity for a hailstone with a diameter of 80 mm.

Show how you obtain your answer.

Give one reason why a hailstone with a large diameter has a greater terminal velocity than a hailstone with a smaller diameter.

Tick (✓) one box.

After falling, the hailstone hits the ground.

Figure 5 shows the forces acting on the hailstone at the moment it hits the ground.

What is the magnitude of the resultant force on the hailstone in Figure 5 ?

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What is the direction of the resultant force on the hailstone in Figure 5 ?

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The relationship between weight and mass for an object can be written as:

Which sentence describes the relationship between weight and mass?

Tick (✓) one box.

Figure 7 shows a balance used to measure the mass of 5 oranges.

All 5 of the oranges have the same mass.

Determine the mass of 1 orange.

Calculate the weight of 1 orange.

gravitational field strength = 9.8 N/kg

Use the equation:

weight = mass × gravitational field strength

The balance shown in Figure 7 contains a spring.

Figure 8 shows the spring with no force acting on it and with a force of 6.0 N acting on it.

Tick (✓) one box.

Use the equation:

What will happen to the spring when the force is removed?

Hailstones are small balls of ice. Hailstones form in clouds and fall to the ground.

Figure 7 shows different-sized hailstones.

A hailstone falls from a cloud and accelerates.

Why does the hailstone accelerate?

The hailstone stops accelerating and reaches terminal velocity.

Explain why the hailstone reaches terminal velocity.

A scientist investigated how the mass of hailstones affects their terminal velocity.

Figure 8 shows the results.

Why does terminal velocity increase with mass?

Tick (✓) one box.

Explain the difference in the maximum kinetic energy of a hailstone with a mass of 10 g and a hailstone with a mass of 20 g.

The kinetic energy of a hailstone is measured in joules.

Which of the following is the same as 1 joule?

Tick (✓) one box.

Figure 8 is repeated below.

A hailstone hit the ground at its terminal velocity of 25 m/s.

The hailstone took 0.060 s to stop moving.

Determine the average force on the hailstone as it hit the ground.

Use information from Figure 8.

Use the Physics Equations Sheet.

Figure 9 shows a balance used to measure the mass of five tomatoes.

What is meant by ‘centre of mass’?

Calculate the mean weight of a tomato in Figure 9.

Use the Physics Equations Sheet.

gravitational field strength = 9.8 N/kg

The balance in Figure 9 contains a spring that compresses when the tomatoes are placed on the balance.

Figure 10 shows the spring with no force acting and with a 6.0 N force acting.

Determine the spring constant of the spring.

Use the Physics Equations Sheet.

Explain one property of the spring that makes it suitable for use in the balance.

The Sun is the closest star to the Earth.

A 2.5 kg mass would have a weight of 750 N at the surface of the Sun. Calculate the gravitational field strength at the surface of the Sun. Use the equation:

Gravity is a non-contact force. Which of the following is also a non-contact force? Tick (✓) one box.

All stars have a life cycle. Figure 15 shows part of the life cycle of a star that becomes a black dwarf. Complete Figure 15. Choose answers from the box.

Black hole Neutron star Red giant Supernova White dwarf

Table 3 gives the mass of three stars compared to the mass of the Sun.

Which letter represents the star most likely to become a black dwarf? Give a reason for your answer. Tick (✓) one box.

In which stage of the life cycle of a star are elements heavier than iron produced? Tick (✓) one box.

A student dropped a piece of modelling clay into oil. Figure 1 shows the modelling clay just before it was dropped into the oil.

What was the distance fallen by the modelling clay? Tick (✓) one box.

What measuring instrument should be used to measure the distance fallen?

The student dropped four pieces of modelling clay, each with a different shape. For each piece the student measured the time taken to fall the same distance through the oil.

The student removed each piece of modelling clay from the oil before dropping the next piece. Suggest one reason why.

The student repeated the measurements and calculated mean values. Table 1 shows the results.

Calculate value X in Table 1.

Each piece of modelling clay had the same mass. Which shape in Table 1 had the smallest resistive force acting against it as it fell? Tick (✓) one box. Give one reason for your answer.

How would the time taken to fall change if the modelling clay was dropped through air instead of through oil? Tick (✓) one box.

The mass of a piece of modelling clay was 0.050 kg. gravitational field strength = 9.8 N/kg Calculate the weight of the piece of modelling clay. Use the equation: weight = mass gravitational field strength

Weight causes the modelling clay to fall through the oil. Weight is a non-contact force. Which of the following are also non-contact forces? Tick (✓) two boxes.

Figure 17 shows four examples of a force causing an object to move.

Which object is not likely to rotate? Tick (✓) one box.

Figure 18 shows a simple device that can be used as a weighing scale. Figure 19 shows the device being used to measure a quantity of rice. The weight of the device is balanced by the weight of the rice and basket. Figure 18 Figure 19

The weight of the device acts through the point labelled X. What is point X called? Tick (✓) one box.

How does Figure 19 show that the weight of the device is balanced by the weight of the rice and basket?

The basket can hang from different points on the device. Where should the basket hang to measure the largest quantity of rice?

Tick (✓) one box.

Write down the equation which links distance, force and moment of a force.

In Figure 19, the weight of the device causes an anticlockwise moment of 0.15 Nm about the pivot. The weight of the rice and basket acts 0.06 m from the pivot.

Calculate the weight of the rice and basket.

Write down the equation which links gravitational field strength, mass and weight.

The basket has a mass of 0.04 kg gravitational field strength = 9.8 N/kg

Calculate the mass of rice in the basket.

Figure 7 shows four blocks of different materials floating on water. The four blocks are the same volume.

Which of the blocks has the smallest weight? Tick one box.

Figure 8 shows a lifebuoy next to a deep swimming pool.

The lifebuoy has a mass of 2.5 kg. gravitational field strength = 9.8 N/kg Calculate the weight of the lifebuoy. Use the equation: weight = mass × gravitational field strength

When thrown into the water the lifebuoy floats. The two forces acting on the lifebuoy are the weight of the lifebuoy downwards and upthrust upwards. How big is the upthrust on the lifebuoy compared to the weight of the lifebuoy? Tick one box.

Write down the equation which links acceleration, mass and resultant force.

A rope is used to pull the lifebuoy to the side of the swimming pool. A resultant force of 4.0 N acts on the lifebuoy. The mass of the lifebuoy is 2.5 kg. Calculate the acceleration of the lifebuoy.

Figure 8 shows a boat floating on the sea. The boat is stationary.

Figure 9 shows part of the free body diagram for the boat. Complete the free body diagram for the boat.

Figure 9

Calculate the mass of the boat. Use the information given in Figure 9. gravitational field strength = 9.8 N/kg Give your answer to two significant figures.

When the boat propeller pushes water backwards, the boat moves forwards. The force on the water causes an equal and opposite force to act on the boat. Which law is this an example of?

Figure 10 shows the boat towing a small dinghy.

Figure 10

The tension force in the tow rope causes a horizontal force forwards and a vertical force upwards on the dinghy. horizontal force forwards = 150 N vertical force upwards = 50 N

Figure 11 shows a grid. Draw a vector diagram to determine the magnitude of the tension force in the tow rope and the direction of the force this causes on the dinghy.

Figure 11

Direction of the force on the dinghy caused