Describing Motion (Edexcel GCSE Physics)

The symbol ‘g’ can be used to refer to the acceleration due to gravity.

The acceleration due to gravity ‘g’ has the unit of m/s².

‘g’ can also have another unit.

Which of these is also a unit for g ?

Two students try to determine a value for g, the acceleration due to gravity.

(i) They measure the time, t, for a small steel ball to fall through a height, h, from rest.

They measure t to be 0.74 s, using a stopwatch.

They measure h to be 2.50 m, using a metre rule.

Calculate a value for g from the students’ measurements.

Use the equation

                     g = .............................................................. m/s²(2)

(ii) They record the time t for two more drops from the same height.

The three values for time t are

0.74 s, 0.69 s, 0.81 s.

Calculate the average value of time t to an appropriate number of significant figures.

average value of time t = ........................................... s(2)

Explain one way the students could improve their procedure to obtain a more accurate value for g.

A car travelling at 15 m/s comes to rest in a distance of 14 m when the brakes are applied.

Calculate the deceleration of the car.

Use an equation selected from the list of equations at the end of this paper.

deceleration = ................................................ m/s²

Figure 1 shows a speed/time graph for a car

Figure 1

(i) The graph in Figure 1 is divided into four parts, P, Q, R and S.

Draw a line from the letter for each part to the correct description of the motion during that part.

One line has been drawn for you. 

(2)

(ii) In two parts of the graph in Figure 1 the forces are balanced.

State the letters of the two parts of the graph where the horizontal forces acting on the car are balanced.  

part .................... and part .......................(2)

(iii) Calculate the distance travelled by the car in part Q.

Use the equation

distance travelled = average speed × time 

distance travelled = ................................ m(2)

A car with a mass of 1800 kg is accelerating at 1.2 m/s².

Calculate the force used to accelerate the car. Use the equation

force = mass × acceleration

force = .......................... N

A train travels at a constant speed of 45.0 m/s.

Calculate the distance it travels in 1.50 minutes.

   Distance = .......................... m

Calculate how long it takes for the same train travelling at the same speed to travel 10.0 km.

Give your answer in minutes.

   Time = .................... minutes

A toy train is made based on the train in parts (a) and (b). The toy train is shown in Figure 1.

A toy sign is placed at the side of the track.

Figure 1

The toy train is powered by a battery and moves along a circular track.

Each lap takes the same amount of time

Compare the speed of the train and the velocity of the train.

The speed-time graph of the model train is shown in Figure 2.

Figure 2

The points at which the train passes the sign are indicated on the graph.

Calculate the circumference of the circular track.

Give your answer to 2 significant figures.

   Circumference = .................... m

A skydiver jumps out of an aeroplane. Their motion is shown on the velocity-time graph in Figure 1.

State the point A, B or C, at which the skydiver's acceleration is greatest.

Explain how you arrived at your answer.

Explain why the equation  cannot be used at points A or B of Figure 1.

The skydiver travels 4000 m in 50 s.

Calculate their average speed.

  Average speed = .................... m/s

State what is represented by the area under a velocity-time graph.

Figure 1 shows a distance-time graph for a train.

Figure 1

State whether the train is travelling faster from A to B or from B to C.

Explain your answer.

Calculate the speed of the train from A to B.

   Speed = .................... m/s

The velocity-time graph of another train is shown in Figure 2.

Figure 2

Calculate the distance travelled in the first 6 hours.

   Distance = .................... km

Suggest why the total displacement after 11 hours is less than your answer to part (c).

i) Which of these is the correct equation that relates force, mass and acceleration?

[1]

ii) A cyclist has a mass of 70 kg.

Calculate the force needed to accelerate the cyclist at 2.0 m/s².

State the unit.

force......................................... unit = ..........................[2]

Another cyclist travels 1200 m in a time of 80 s.

Calculate the average speed of the cyclist.

Use the equation

average speed = ............................ m/s

A student wants to measure the average speed of a cyclist.

The student estimates that one of his own steps is 1 m.

He counts 100 steps between two posts on a track.

He uses a stopwatch to measure the time the cyclist takes to travel between the two posts.

Figure 2 shows the set‐up used to measure the average speed.

Figure 2

State two improvements the student could make to this method.

1...............................................................................................

2...............................................................................................

i) Which of these would be a typical speed for a racing cyclist travelling down a steep straight slope?

  [1]

ii) A cyclist travels down a slope.

The top of the slope is 20 m vertically above the bottom of the slope.

The cyclist has a mass of 75 kg.

Calculate the change in gravitational potential energy of the cyclist between the top and the bottom of the slope.

The gravitational field strength, g, is 10 N/kg. 

change in gravitational potential energy =.......................... J [3]

An aircraft waits at the start of a runway.

The aircraft accelerates from a speed of 0 m/s to a speed of 80 m/s.

The acceleration of the aircraft is 4 m/s².

Calculate the distance, x, travelled by the aircraft while it is accelerating.

Use the equation  

x =.......................m

A student needs to measure the average speed of an accelerating trolley between two marks on a bench.

Figure 5 shows the arrangement of some apparatus that the student can use. 

Figure 5

i) One piece of apparatus is missing from the diagram.

This piece of apparatus is needed to determine the average speed.

State the extra piece of apparatus needed to determine the average speed.

[1] 

ii) Describe how the student can make the trolley accelerate along the bench.

[2] 

iii) The student wishes to develop the experiment to determine the acceleration of the trolley.

State one other measurement that the student must make to determine the acceleration of the trolley.  

[1] 

Which of these graphs represents an object moving with a constant velocity of 2 m/s?

Figure 8 is a velocity/time graph showing a 34 s part of a train’s journey.

Figure 8

i) Calculate the acceleration of the train in the 34 s.

Give your answer to an appropriate number of significant figures.

acceleration = ............................................... m/s² [3] 

ii) Calculate the distance the train travels in the 34 s.

distance ............................................................. m[3]

Figure 9 shows a rocket soon after it takes off from the ground.

Figure 9

The force that the rocket engines produce remains constant during the first few seconds after take-off.

Explain what happens to the acceleration during the first few seconds.

Quantities can be either scalar or vector.

Which of these is a vector quantity?

Figure 7 shows a ball bearing as it falls slowly through a clear, dense liquid.

Figure 7

The apparatus in Figure 7 is used to find the average speed of the ball bearing as it falls.

i) Devise an experiment to determine the average speed of the ball bearing as it falls through the liquid.

You should include:

• any extra apparatus you would use to take measurements

• the measurements you would take

• how you would calculate the speed.

[4] 

ii) A student thinks that the ball bearing falls through the liquid at a constant speed.

Explain how you could develop this experiment to determine if the ball bearing falls through the liquid at constant speed.

You may draw a diagram to help your answer.

[2] 

The ball bearing is now dropped through air.

The initial velocity of the ball bearing is zero.

The acceleration of the ball bearing is 10 m/s².

The ball bearing falls 1.5 m.

Calculate the velocity of the ball bearing when it has fallen 1.5 m. Use the equation

velocity of ball bearing = ................................. m/s

Which of these is a vector?

i) State the equation that relates acceleration to change in velocity and time taken. 

[1] 

ii) A van accelerates from a velocity of 2 m/s to a velocity of 20 m/s in 12 s.

Calculate the acceleration of the van.

 acceleration = ....................................... m/s² [2]

Figure 3 is a velocity /time graph for 15 s of a cyclist’s journey.

Figure 3

i) Calculate the distance the cyclist travels in the 15 s.

 distance = ....................................................... m[3]

ii) Another cyclist starts from rest, but his acceleration decreases as time increases.

Sketch the velocity / time graph for this cyclist on Figure 3.

[2]