Contact & non-contact forces

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 student investigated how changing the mass of a trolley affects the acceleration of the trolley.

Figure 5 shows some of the equipment used.

The trolley in Figure 5 is not moving.

Which force prevents the trolley from moving?

Tick (✓) one box.

The force pulling on the trolley was increased so that the trolley accelerated.

The force was then kept constant and different masses were put on the trolley.

For each different mass the acceleration of the trolley was measured.

Draw one line from each variable to the correct quantity.

For one of the masses put on the trolley, the student recorded three values of acceleration.

Calculate the mean acceleration of the trolley.

Figure 6 shows some of the results.

Describe the relationship shown in Figure 6.

When the total mass of the trolley was 1.5 kg, the acceleration of the trolley

Calculate the resultant force acting on the trolley.

Use the equation:

resultant force = mass × acceleration

A student investigated how the acceleration of a trolley varies with the resultant force on the trolley.

Figure 10 shows some of the equipment used.

Figure 10 shows the force F which acts through the string.

What name is given to force F ?

Give one variable that should have been a control variable in this investigation.

The student held the trolley stationary and then released it.

The trolley moved along the runway with a constant acceleration.

The student recorded the time taken for the trolley to travel a measured distance along the runway.

Describe how the acceleration of the trolley can be calculated using the time taken and distance travelled by the trolley.

For one set of results, the force acting through the string was 2.0 N.

The student released the trolley three times and determined the following values for acceleration:

Calculate the uncertainty in the values of acceleration.

The runway was then raised at one end.

The force acting through the string remained the same.

Figure 11 shows this.

Explain how the acceleration was affected by raising the end of the runway.

Figure 25 shows the route an aeroplane takes as it travels from an airport terminal to the runway. Figure 25 has been drawn to scale.

Determine the magnitude of the aeroplane’s displacement from the start point to the finish point on Figure 25.

Figure 26 shows the direction of the horizontal forces acting on the aeroplane as it moves in a straight line towards the runway.

Determine the magnitude of the resultant horizontal force on the aeroplane.

Describe the motion of the aeroplane as it moves towards the runway.

Air resistance and friction are contact forces. Give one other example of a contact force.

The aeroplane stops for a short time and then accelerates along the runway. Figure 27 shows a distance–time sketch-graph for this stage of the journey.

Draw the velocity–time sketch-graph for this stage of the journey on Figure 28.

The aeroplane takes off from the runway, so its height above the ground increases. Figure 29 shows how atmospheric pressure varies with the height of the aeroplane above the ground.

Estimate the atmospheric pressure when the height of the aeroplane above the ground is 10 km.

What happens to the air surrounding the aeroplane as the height of the aeroplane above the ground increases? Tick (✓) one box.

Figure 3 shows the route an aeroplane takes as it travels from an airport terminal to the runway. Figure 3 has been drawn to scale.

Determine the magnitude of the aeroplane’s displacement from the start point to the finish point on Figure 3.

Figure 4 shows the direction of the horizontal forces acting on the aeroplane as it moves in a straight line towards the runway.

Determine the magnitude of the resultant horizontal force on the aeroplane.

Describe the motion of the aeroplane as it moves towards the runway.

Air resistance and friction are contact forces. Give one other example of a contact force.

The aeroplane stops for a short time and then accelerates along the runway. Figure 5 shows a distance–time sketch-graph for this stage of the journey.

Draw the velocity–time sketch-graph for this stage of the journey on Figure 6.

The aeroplane takes off from the runway, so its height above the ground increases. Figure 7 shows how atmospheric pressure varies with the height of the aeroplane above the ground.

Estimate the atmospheric pressure when the height of the aeroplane above the ground is 10 km.

What happens to the air surrounding the aeroplane as the height of the aeroplane above the ground increases? Tick (✓) one box.

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.

Figure 11 shows a cyclist riding a bicycle. Force A causes the bicycle to accelerate forwards.

What name is given to force A ?

Figure 12 shows how the velocity of the cyclist changes during a short journey.

Determine the distance travelled by the cyclist between Y and Z.

Figure 13 shows the gears on the bicycle.

Describe how the force on the pedal causes a moment about the rear axle.

Figure 14 shows a different cyclist towing a trailer.

The speed of the cyclist and trailer increased uniformly from 0 m/s to 2.4 m/s. The cyclist travelled 0.018 km while accelerating. Calculate the initial acceleration of the cyclist.

The resultant force of the towbar on the trailer has a horizontal component and a vertical component. horizontal force = 200 N vertical force = 75 N

Determine the magnitude and direction of the resultant force of the towbar on the trailer by drawing a vector diagram.

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.