Download 1. A skydiver of mass 80 kg falls vertically with a constant

1.
A skydiver of mass 80 kg falls vertically with a constant speed of 50 m s–1. The upward force
acting on the skydiver is approximately
A.
0 N.
B.
80 N.
C.
800 N.
D.
4000 N.
(Total 1 mark)
2.
A car of mass 1000 kg accelerates on a straight, flat, horizontal road with an acceleration
a = 0.3 m s–2.
The driving force F on the car is opposed by a resistive force of 500 N.
The net (resultant) force on the car is
A.
200 N.
B.
300 N.
C.
500 N.
D.
800 N.
(Total 1 mark)
3.
Which of the following is the condition for a body to be in translational equilibrium?
A.
The resultant force on the body in any direction is zero.
B.
The velocity of the body in any direction is zero.
C.
No external force is acting on the body.
D.
No work is done on the body.
(Total 1 mark)
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4.
A wooden block is sliding down an inclined plane at constant speed. The magnitude of the
frictional force between the block and the plane is equal to
A.
zero.
B.
the magnitude of the weight of the block.
C.
the magnitude of the component of weight of the block parallel to the plane.
D.
the magnitude of the component of the normal reaction parallel to the plane.
(Total 1 mark)
5.
Which of the following is a correct statement of Newton’s second law of motion?
A.
A force acting on a body is proportional to the mass of the body.
B.
The rate of change of momentum of a body is equal to the net external force acting on the
body.
C.
The momentum of a body is proportional to the net external force acting on the body.
D.
A force acting on a body is proportional to the acceleration of the body.
(Total 1 mark)
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6.
Stephen pushes two boxes P and Q, that stay in contact, along a rough table, with a force F of
30 N.
Box P has a mass of 2.0 kg and box Q has a mass of 4.0 kg. Both boxes move with constant
speed.
The resultant force on box Q is
A.
0 N.
B.
5.0 N.
C.
15 N.
D.
30 N.
(Total 1 mark)
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7.
A cart of mass M is on a horizontal frictionless table.
The cart is connected to an object of weight W via a pulley. Which of the following is the
acceleration of the cart?
M
A.
W
g
W
W
B.
M
C.
Mg
W
D.
0
W
g
(Total 1 mark)
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8.
Two steel balls, of mass M and 2M, fall at constant speeds in a tube filled with oil.
Which of the following correctly compares the magnitudes of the net force and of the drag
(resistance) force on the two balls?
Net force
Drag force
A.
same
same
B.
same
different
C.
different
same
D.
different
different
(Total 1 mark)
9.
A skydiver jumped out of an airplane. On reaching a terminal speed of 60 m s–1, she opened her
parachute. Which of the following describes her motion after opening her parachute?
A.
She went upwards for a short time, before falling to Earth at a speed of 60 m s–1.
B.
She continued downwards at 60 m s–1, but hit the ground with less force.
C.
She continued to fall but reached a new terminal speed of less than 60 m s–1.
D.
She went upwards for a short time, before falling to Earth at a speed of less than 60 m
s–1.
(Total 1 mark)
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10.
The diagram shows a girl attempting (but failing) to lift a heavy suitcase of weight W. The
magnitude of the vertical upwards pull of the girl on the suitcase is P and the magnitude of the
vertical reaction of the floor on the suitcase is R.
Which equation correctly relates W, P and R?
A.
W=P+R
B.
W>P+R
C.
W<P+R
D.
W=P=R
(Total 1 mark)
11.
Objects A and B collide together. They end up joined together and stationary. During the
collision, a force +F is exerted on object A by object B. According to Newton’s third law, there
will also be a force of
A.
–F acting on object B.
B.
–F acting on object A.
C.
+F acting on object B.
D.
+F acting on object A.
(Total 1 mark)
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12.
A student is sitting on a chair. One force that is acting on the student is the pull of gravity.
According to Newton’s third law, there must be another force which is
A.
the upward push of the chair on the student.
B.
the downward force on the student.
C.
the downward push of the chair on Earth.
D.
the upward force on Earth.
(Total 1 mark)
13.
A lamp of weight W is suspended by a wire fixed to the ceiling. With reference to Newton’s
third law of motion, the force that is equal and opposite to W is the
A.
tension in the wire.
B.
force applied by the ceiling.
C.
force exerted by the lamp on the Earth.
D.
force exerted by the Earth on the lamp.
(Total 1 mark)
14.
If a moving object is subject to a constant force, which of the following can be correctly
deduced from Newton’s first law?
A.
The object continues to move with a changing velocity.
B.
The object continues to move with a constant velocity.
C.
The object continues to move with a changing direction.
D.
The object continues to move in the same direction.
(Total 1 mark)
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15.
Mandy stands on a weighing scale inside a lift (elevator) that accelerates vertically upwards as
shown in the diagram below. The forces on Mandy are her weight W and the reaction force
from the scale R.
The reading of the scale is
A.
R + W.
B.
W.
C.
R.
D.
R – W.
(Total 1 mark)
16.
A frictionless trolley of mass m moves down a slope with a constant acceleration a. A second
similar frictionless trolley has mass 2m. The acceleration of the second trolley as it moves
down the slope is
A.
1
a.
2
B.
a.
C.
2a.
D.
4a.
(Total 1 mark)
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17.
A spacecraft orbits Earth. An astronaut inside the spacecraft feels “weightless” because
A.
the gravitational field in the spacecraft is negligible.
B.
the Earth exerts equal forces on the spacecraft and the astronaut.
C.
the spacecraft and the astronaut have the same acceleration towards the Earth.
D.
the spacecraft and the astronaut exert equal and opposite forces on each other.
(Total 1 mark)
18.
This question is about force and energies.
(a)
A system consists of a bicycle and cyclist travelling at a constant velocity along a
horizontal road.
(i)
State the value of the net force acting on the cyclist.
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(1)
(ii)
On the diagram draw labelled arrows to represent the vertical forces acting on the
bicycle.
(2)
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(iii)
With reference to the horizontal forces acting on the system, explain why the
system is travelling at constant velocity.
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(2)
(b)
The total resistive force acting on the system is 40 N and its speed is 8.0 m s–1. Calculate
the useful power output of the cyclist.
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(1)
(c)
The cyclist stops pedalling and the system comes to rest. The total mass of the system is
70 kg.
(i)
Calculate the magnitude of the initial acceleration of the system.
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(2)
(ii)
Estimate the distance taken by the system to come to rest from the time the cyclist
stops pedalling.
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(2)
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(iii)
State and explain one reason why your answer to (c)(ii) is only an estimate.
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(2)
(Total 12 marks)
19.
This question is about mechanics and thermal physics.
The graph shows the variation with time t of the speed v of a ball of mass 0.50 kg, that has been
released from rest above the Earth’s surface.
The force of air resistance is not negligible. Assume that the acceleration of free fall is
g = 9.81 m s–2.
(a)
State, without any calculations, how the graph could be used to determine the distance
fallen.
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(1)
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(b)
(i)
In the space below, draw and label arrows to represent the forces on the ball at
2.0 s.
(1)
(ii)
Use the graph opposite to show that the acceleration of the ball at 2.0 s is
approximately 4 m s–2.
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(2)
(iii)
Calculate the magnitude of the force of air resistance on the ball at 2.0 s.
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(2)
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(iv)
State and explain whether the air resistance on the ball at t = 5.0 s is smaller than,
equal to or greater than the air resistance at t = 2.0 s.
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(2)
(c)
After 10 s the ball has fallen 190 m.
(i)
Show that the sum of the potential and kinetic energies of the ball has decreased by
780 J.
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(3)
(ii)
The specific heat capacity of the ball is 480 J kg–1 K–1. Estimate the increase in the
temperature of the ball.
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(2)
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(iii)
State an assumption made in the estimate in (c)(ii).
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(1)
(Total 14 marks)
20.
This question is about motion of a ball falling in oil.
(a)
Distinguish between average speed and instantaneous speed.
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(2)
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(b)
A small steel ball of mass M is dropped from rest into a long vertical tube that contains
oil.
The sketch graph shows how the speed v of the ball varies with time t.
Explain how you would use the graph to find the average speed of the ball between t = 0
and t = t1.
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(3)
(c)
The gradient of the graph at t = t1 is k. Deduce an expression in terms of k, M and g, the
acceleration of free fall, for the magnitude of the frictional force F acting on the ball at t
= t1 .
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(3)
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(d)
State and explain the magnitude of the frictional force acting on the ball at t = t2.
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(3)
(Total 11 marks)
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