P2 Revision Booklet

Force and Acceleration

Medium (Grade C)

Q1.The diagram shows the forces acting on a car. The car is being driven along a straight, level road at a constant speed of 12 m/s.

(a)     The driver then accelerates the car to 23 m/s in 4 seconds.
Use the equation in the box to calculate the acceleration of the car.

Show clearly how you work out your answer and give the unit.
........................................................................................................................
........................................................................................................................
    Acceleration = ...................................................................................
(3)

(b)     Describe how the horizontal forces acting on the car change during the first two seconds of the acceleration.
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........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(Total 6 marks)

 Q2.          (a)     The diagram shows an athlete at the start of a race. The race is along a straight track.

          In the first 2 seconds, the athlete accelerates constantly and reaches a speed of 9 m/s.

(i)      Use the equation in the box to calculate the acceleration of the athlete.

         Show clearly how you work out your answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Acceleration = ..............................
(2)

(ii)     Which one of the following is the unit for acceleration?
         Draw a ring around your answer.
         J/s                   m/s                       m/s2                      Nm
(1)

(iii)     Complete the following sentence.
         The velocity of the athlete is the .................................................................... of the
         athlete in a given direction.
(1)

(iv)    Complete the graph to show how the velocity of the athlete changes during the first 2 seconds of the race.

(2)

(b)     Many running shoes have a cushioning system. This reduces the impact force on the athlete as the heel of the running shoe hits the ground.

          The bar chart shows the maximum impact force for three different makes of running shoe used on three different types of surface.

(i)      Which one of the three makes of running shoe, A, B or C, has the best cushioning system?
...........................................................................................................................
         Explain the reason for your answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)

(ii)     The data needed to draw the bar chart was obtained using a robotic athlete fitted with electronic sensors.
         Why is this data likely to be more reliable than data obtained using human athletes?
...........................................................................................................................
...........................................................................................................................
(1)
(Total 10 marks)
Q3.          The diagram below shows an empty cargo ship. It is not moving.

(a)     The water exerts a force on the ship. In which direction does this force act?
.....................................................................................................................................
(1)

(b)     The diagram below shows the same cargo ship. This time it has a full load of cargo.

(i)      How does the force exerted by the water on the ship change as the ship is loaded?
         ...........................................................................................................................
(1)

(ii)     Why has the force exerted by the water changed?
         ...........................................................................................................................
(1)
(Total 3 marks)

 

Q4.          

          Five forces, A, B, C, D and E act on the van.

(a)     Complete the following sentences by choosing the correct forces from A to E.
          Force ................ is the forward force from the engine.
          Force ................ is the force resisting the van’s motion.
(1)

(b)     The size of forces A and E can change.
Complete the table to show how big force A is compared to force E for each motion of the van.
Do this by placing a tick in the correct box.
The first one has been done for you.
MOTION OF VAN	FORCE A SMALLER
THAN FORCE E	FORCE A EQUAL
TO FORCE E	FORCE A BIGGER
THAN FORCE E	
Not moving 	 		 	
Speeding up	 	 	 	
Constant speed	 	 	 	
Slowing down	 	 	 	

(3)

(c)     When is force E zero?
....................................................................................................................................
(1)

(d)     The van has a fault and leaks one drop of oil every second.
The diagram below shows the oil drops left on the road as the van moves from W to Z.

          Describe the motion of the van as it moves from:
W to X ........................................................................................................................
X to Y .........................................................................................................................
Y to Z ..........................................................................................................................
(3)

(e)     The driver and passengers wear seatbelts.
Seatbelts reduce the risk of injury if the van stops suddenly.
backwards      downwards        force           forwards       mass      weight
          Complete the following sentences, using words from the list above, to explain why the risk of injury is reduced if the van stops suddenly.
          A large ........................................ is needed to stop the van suddenly.
          The driver and passengers would continue to move ............................................... .
          The seatbelts supply a ........................................ force to keep the driver and passengers
          in their seats.
(3)
(Total 11 marks)
Q5.          (a)     The arrows in the diagram represent the size and direction of the forces on a space shuttle, fuel tank and booster rockets one second after launch. The longer the arrow the bigger the force.
         Thrust force

          Weight of shuttle, fuel tanks and
booster rockets plus air resistance

(i)      Describe the upward motion of the space shuttle one second after launch.
...........................................................................................................................
(1)

(ii)     By the time it moves out of the Earth’s atmosphere, the total weight of the space shuttle, fuel tank and booster rockets has decreased and so has the air resistance.
         How does this change the motion of the space shuttle? (Assume the thrust force does not change).
...........................................................................................................................
(1)

(b)     The space shuttle takes 9 minutes to reach its orbital velocity of 8100 m/s.
(i)      Write down the equation that links acceleration, change in velocity and time taken.
...........................................................................................................................
(1)

(ii)     Calculate, in m/s2, the average acceleration of the space shuttle during the first 9 minutes of its flight. Show clearly how you work out your answer.
...........................................................................................................................
...........................................................................................................................
average acceleration = .............................................. m/s2
(2)

(iii)     How is the velocity of an object different from the speed of an object?
...........................................................................................................................
...........................................................................................................................
(1)
(Total 6 marks)

 

Q6.          

(a)     The van shown above has a fault and leaks one drop of oil every second.
          The diagram below shows the oil drops left on the road as the van moves from W to Z.

          Describe the motion of the van as it moves from:
W to X .......................................................................................................................
....................................................................................................................................
X to Y ........................................................................................................................
....................................................................................................................................
Y to Z ........................................................................................................................
....................................................................................................................................
(3)

(b)     The van was driven for 20 seconds at a speed of 30m/s.
          Calculate the distance travelled.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Distance .................... m
(2)

(c)     The van was travelling at 30m/s. It slowed to a stop in 12 seconds.
          Calculate the van’s acceleration.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Acceleration .................... m/s²
(3)

(d)     The driver and passenger wear seatbelts. Seatbelts reduce the risk of injury.
          Explain how seatbelts reduce the risk of injury.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(Total 12 marks)
Q7.          

          In a science lesson, some children float an apple on some water.
          One of the children says:
          “The apple is not moving. That means that there cannot be any forces acting on it.”
          Do you agree?
Explain your answer as fully as you can.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(Total 3 marks)
Q8.          The diagram shows a shuttlecock that is used for playing badminton.

          The shuttlecock weighs very little.
When you drop it from a height of a few metres, it accelerates at first but soon reaches a steady speed.

          Explain, as fully as you can:
(a)     why the shuttlecock accelerates at first,
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)

(b)     why the shuttlecock reaches a steady speed. 
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...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(3)
(Total 5 marks)
 Forces and acceleration-Mark scheme

M1.         (a)     2.75
allow 1 mark for correct substitution, ie 
or  
provided no subsequent step shown
2

m/s2
1

(b)     driving force increases
1

frictional force increases
accept air resistance / drag for frictional force
1

driving force > frictional force 
1
[6]
 
M2.          (a)     (i)      4.5
allow 1 mark for correct substitution i.e. 9 ÷ 2
2

(ii)     m/s2
accept answer given in (a)(i) if not contradicted here
1

(iii)     speed
1
(iv)    straight line from the origin passing through (2s, 9m/s)
allow 1 mark for straight line from the origin passing through to t = 2 seconds
allow 1 mark for an attempt to draw a straight line from the origin passing through (2,9)
allow 1 mark for a minimum of 3 points plotted with no line provided if joined up would give correct answer. Points must
include(0,0) and (2,9)
2

(b)     (i)      B
if A or C given scores 0 marks in total
1
         smallest (impact) force
1
         on all/ every/ any surfaces
these marks are awarded for comparative answers
1

(ii)     (conditions) can be repeated
         or
         difficult to measure forces with human athletes
accept answers in terms of variations in human athletes e.g.
athletes may have different weights area / size of feet may be different difficult to measure forces athletes run at different speeds
accept any answer that states or implies that with humans the conditions needed to repeat tests may not be constant
e.g.
athletes unable to maintain constant speed during tests (or during repeat tests)
do not accept the robots are more accurate
removes human error is insufficient
fair test is insufficient
1
[10]
 M3.          (a)     up
for 1 mark
1

(b)     (i)      increased
for 1 mark
1
(ii)     more water displaced; ship heavier
either for 1 mark
1
[3]
 M4.          (a)     A then E
for one mark
1

(b)     A > E
A = E
A < E 
in this order for 1 mark each
3

(c)     when van stops / is stationary / is parked
for one mark
1

(d)     WX – slowing down (owtte)
XY – constant speed (owtte)
YZ – speeding up (owtte)
for 1 mark each
3
(e)     ….. force …. forwards …. backwards
for 1 mark each
3
[11]
 M5.          (a)     (i)      accelerating
accept getting faster
accept speed / velocity increasing
1
(ii)     acceleration increases
accept velocity / speed increases more rapidly
do not accept velocity / speed increases
1

(b)     (i)      acceleration = 
 
accept a =  or a = 
 
do not accept velocity for change in velocity
do not accept change in speed
do not accept a = 
1
(ii)     15
allow 1 mark for an answer of 900 or  for correct use of 540 seconds
2
(iii)     velocity includes direction
accept velocity is a vector (quantity)
accept converse answer
1
[6]

M6.          (a)     WX deceleration / speed decreasing / slowing down / negative acceleration
          XY constant speed / steady speed not constant motion / slow speed
          YZ acceleration / speed increasing / speeding up
for 1 mark each
3

(b)     distance = v × t       or       distance = 30 × 20
gains 1 mark
          but
distance = 600(m)
gains 2 marks
2

(c)     acceleration = v / t    or       acceleration = 30 / 12
gains 1 mark
(if –30 / 12, allow negative sign here if not in the answer)
3
          but
acceleration  = 2.5 (m/s²)
gains 2 marks
          but
acceleration = -2.5 (m/s²)
gains 3 marks

(d)     in a crash / during hard braking car body stops / slows rapidly driver / passengers continue to move forward not thrown forward seatbelts provide backward force / keep them in their seats / restrain them to stop them hitting the windscreen / dashboard
(an alternative argument involving momentum is acceptable) 
for 1 mark each
4
[12
##
          ideas that
gravity/weight (downwards)
upwards/opposite  force of water  or  upthrust
forces are balanced
any three for 1 mark each
          (N.B. All these ideas may be included in a short response)
          (If no marks gained but candidate makes reference to forces, award 1 mark)
[3]
 M8.          (a)     reference to
•        weight / force of gravity / acting downwards
•        unbalanced (by any upwards force)
for 1 mark each
2

(b)     ideas that forces balance(d)
gains 1 mark
          but
weight / force of gravity / downwards force balanced by friction / air 
resistance / drag / upwards force
gains 2 marks
          latter increases with speed
          (accept arrows or relevant length and direction if clearly labelled,
as answers to parts (a) and (b))
for 1 further mark
3
[5]