Q1. A bus is taking some children to school.
(a)     The bus has to stop a few times. The figure below shows the distance–time graph for part of the journey.
 
                        Time in seconds
(i)      How far has the bus travelled in the first 20 seconds?
Distance travelled = ______________________ m
(1)
(ii)     Describe the motion of the bus between 20 seconds and 30 seconds.
______________________________________________________________
______________________________________________________________
(1)
(iii)    Describe the motion of the bus between 30 seconds and 60 seconds.
Tick () one box.
 
 	Tick ()	
Accelerating	 	
Reversing	 	
Travelling at constant speed	 	
(1)
(iv)    What is the speed of the bus at 45 seconds?
Show clearly on the figure above how you obtained your answer.
______________________________________________________________
______________________________________________________________
______________________________________________________________
Speed = ______________________ m / s
(3)
(b)     Later in the journey, the bus is moving and has 500 000 J of kinetic energy.
The brakes are applied and the bus stops.
(i)      How much work is needed to stop the bus?
______________________________________________________________
Work = ______________________ J
(1)
(ii)     The bus stopped in a distance of 25 m.
Calculate the force that was needed to stop the bus.
______________________________________________________________
______________________________________________________________
Force = ______________________ N
(2)
(iii)    What happens to the kinetic energy of the bus as it is braking?
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(Total 11 marks)

Mark schemes
Q1.
(a)     (i)      100 (m)
1
(ii)     stationary
1
(iii)     accelerating
1
(iv)    tangent drawn at t = 45 s
1
attempt to determine slope
1
speed in the range 3.2 – 4.2 (m / s)
dependent on 1st marking point
1
(b)     (i)      500 000 (J)
ignore negative sign
1
(ii)     20 000 (N)
ignore negative sign
allow 1 mark for correct substitution, ie
500 000 = F  ×  25
or their part (b)(i) = F  ×  25
provided no subsequent step
2
(iii)    (kinetic) energy transferred by heating
1
to the brakes
ignore references to sound energy
if no other marks scored allow k.e. decreases for 1 mark
1
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