Motion (Cambridge O Level Physics)

Model trains move along a track passing through two model stations. Students analyse the motion of a train. They start a digital timer as the train starts to move. They record the time that it enters Station A and the time it enters Station B.

Fig 1.1 below shows the time on entering Station A and the time on entering Station B.

Calculate the time taken from the train entering Station A to the train entering Station B.
State your answer in seconds.

time taken = ....................................................... s 

A faster train takes 54 s to travel from Station A to Station B. The distance between the stations is 120 m.

Calculate the average speed of this train.

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

Fig. 1.2 shows the speed-time graph for a train travelling on a different part of the track.

Define acceleration.

Some cyclists are racing around a track. 

Fig.2.1 shows the speed-time graph for one cyclist.

(i)

Tick the box that represents the cyclist travelling at constant speed.

A

B

C

D

[1]

The length of the track is 250m. 

 Another cyclist goes around the track four times (four laps). This takes 80.0 seconds.

Fig. 1.1 shows the speed–time graph of a person on a journey.

On the journey, he walks and then waits for a bus. He then travels by bus. He gets off the bus and waits for two minutes. He then walks again. His journey takes 74 minutes.

For the whole journey calculate:

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

average speed = ......................................................... [2]

State and explain which feature of a speed–time graph shows acceleration.

State and explain the acceleration of the person at time = 40 minutes.

A person on roller skates makes a journey. Fig. 1.1 shows the speed-time graph for the journey.

The graph shows three types of motion.

Complete the table to show when each type of motion occurs. Use the letters shown on Fig. 1.1. Add a letter to each of the blank spaces. The first row is done for you.

Calculate the distance travelled between 60 s and 100 s.

The size of the acceleration is greater than the deceleration.

Describe how Fig. 1.1 shows this.

A student uses a stopwatch to determine the time between two drops hitting the ground.

He sets the stopwatch to zero. He starts the stopwatch when the first drop hits the ground.

He stops the stopwatch after a further 30 drops have hit the ground.

The reading on the stopwatch is recorded and shown in Fig. 1.2.

 time = ...................................................... s [1]

 time = ...................................................... s [2]

[1]

Fig. 1.1 shows that the drops get further apart as they get close to the ground.

State why the drops get further apart.

In another experiment the student determines the speed of a falling weight at different times. The speed–time graph for his results is shown in Fig. 1.3.

Calculate the distance fallen by the weight in the first 1.5 s.

A lorry is travelling along a straight, horizontal road.
Fig. 1.1 is the distance-time graph for the lorry.

Using Fig. 1.1, determine:

At time t = 30s, the total resistive force acting on the lorry is 1.4 × 10⁴ N.

Describe the motion of the lorry between time t = 60 s and time t = 130 s.

An athlete runs 12 km in 1.5 hours.

Calculate the athlete’s average speed in km/h.

Fig. 2.1 shows the speed-time graph for a footballer for the first 15.0 seconds of a game.

Another footballer has a mass of 72kg.

Calculate the weight of this footballer.

An aircraft flies at a constant height.

Air drag and the force from the aircraft’s engines together produce a force on the aircraft of 36 kN due north, as shown in Fig. 1.1.

The wind produces a force of 12 kN towards the east.

Fig 1.1

Draw a scale drawing to show the resultant force acting on the aircraft.

Use your drawing to determine the size of the resultant force and the angle between the resultant force and north.

Fig. 1.1 is the speed-time graph for a stone as it falls to the ground.

Fig. 1.1

[2]

[1]

The weight of the stone is 4.0 N.
 
As the stone falls, the force F of air resistance acting on the rock changes.

F = ......................................................  N [1]

F = ......................................................  N [1]
 

(iii) Suggest why F changes between t = 0 s and t = 10.0 s

 [1]

acceleration = ..................................... unit = .......... [3]
 

F = ......................................................  N [2]

A student drops a ball from a high window.

The mass of the ball is 0.12 kg.

Calculate the weight of the ball.

weight = .................................................... N

Fig. 3.1 shows the speed of the ball while it is falling. The points S, T, U, V and W are shown on the graph.

Draw one line from each section of the graph to the correct description of the motion.

One has been drawn for you.

Determine the distance fallen by the ball in section U – V of the graph.

distance = .................................................... m 

State the distance fallen by the ball in section V – W of the graph.

   
distance = .................................................... m 

A rocket is launched vertically upwards from the ground. The rocket travels with uniform acceleration from rest. After 8.0 s, the speed of the rocket is 120 m/s.

Calculate the acceleration of the rocket.

 
acceleration = ........................................................ m/s² 

(i)

On Fig. 1.1, draw the graph for the motion of the rocket in the first 8.0 s.

 

[1]

Fig. 1.1 shows a speed-time graph for a student who is running.

Fig. 1.1

An athlete runs 630 m in 130 s on a flat section of a road and then 254 m in 40 s on a downhill slope.

Calculate the average speed for the total distance run by the athlete.

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

A train of mass 5.6 × 10⁵ kg is at rest in a station.

At time t = 0 s, a resultant force acts on the train and it starts to accelerate forwards.

Fig. 1.1 is the distance-time graph for the train for the first 120 s.

A rocket is stationary on the launchpad. At time t = 0, the rocket engines are switched on and exhaust gases are ejected from the nozzles of the engines. The rocket accelerates upwards.

Fig. 1.1 shows how the acceleration of the rocket varies between time t = 0 and time t = t_f.

Define acceleration.

On Fig. 1.2, sketch a graph to show how the speed of the rocket varies between time t = 0 and time t = t_f.

A student watches a car race around a track. He uses a stopwatch to measure the time for the car to make one lap of the track.

The student forgets to reset the stopwatch at the start of the race. Fig. 1.1 shows the time on the stopwatch at the start and the time after going around the track once.

Calculate the time the car takes to go around the track once, in seconds.
 

The length of the track is 4.0 km. The car goes around the track 20 times. The car takes 26 minutes and 40 seconds to complete the 20 laps.

Calculate the average speed of the car in m / s.

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

Fig. 1.2 shows a speed-time graph for the car during part of the race.

Fig. 1.1 shows the speed-time graph for a vehicle accelerating from rest.

Calculate the acceleration of the vehicle at time = 30s.

acceleration = ...........................................................

Determine the distance travelled by the vehicle between time = 120 s and time = 160 s.

distance = ........................................................... 

Define acceleration.

Fig. 1.1 shows two speed–time graphs, A and B, and two distance–time graphs, C and D.

Describe the motion shown by:

Extended

Fig. 1.1 shows the axes of a distance-time graph for an object moving in a straight line.

Fig. 1.2 shows the axes of a speed-time graph for a different object.

Fig. 2.1 shows students getting onto a school bus.

A student describes part of the journey.

The bus accelerates from rest at a constant rate for 10 s. It reaches a maximum speed of 10 m/s.

The bus maintains a constant speed of 10 m/s for 60 s.

The bus then decelerates at a constant rate for 15 s, until it stops.

On Fig. 2.2, draw the speed-time graph for this part of the journey made by the bus.

On another part of the journey, the average speed of the bus is 7.5 m/s.

Calculate the distance the bus travels in 150 s.

distance = ..................................................... m