Name………………………
Mechanics practice exam questions
1.	The graph shows the variation with time t of the velocity v of an object.

	Which one of the following graphs best represents the variation with time t of the acceleration a of the object?

(1)

2.	A ball, initially at rest, takes time t to fall through a vertical distance h. If air resistance is ignored, the time taken for the ball to fall from rest through a vertical distance 9h is
A.	3t.
B.	5t.
C.	9t.
D.	10t.
(1)

3.	A raindrop falling through air reaches a terminal velocity before hitting the ground. At terminal velocity, the frictional force on the raindrop is
A.	zero.
B.	less than the weight of the raindrop.
C.	greater than the weight of the raindrop.
D.	equal to the weight of the raindrop.
(1)

4.	This question is about a wooden block sliding down a rough inclined plane (slope).
	The diagram below shows a wooden block sliding down a rough plane. In the position shown the block is accelerating.

(a)	Draw a free-body diagram representing the forces acting on the block.

(4)
	The plane makes an angle of 60° with the horizontal, the weight of the block is 5.0 N and the coefficient of kinetic (dynamic) friction between the block and the plane is 0.30.
(b)	(i)	Determine the magnitude of the frictional force acting on the block.
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(2)
(ii)	Determine the acceleration of the block down the plane.
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(2)
(Total 8 marks)

5.	The diagram below shows the path of a projectile in the absence of air resistance.

	Which one of the following diagrams best represents the path of the projectile under the same initial conditions when the air resistance is taken into account? (The path in absence of air resistance is shown for comparison as a dotted line.)

(1)

6.	A sailing boat is moving with constant velocity v to the right parallel to the dock.

	Sailor Hulot, up on the mast, drops his telescope at the moment he is opposite Lucie who is standing on the dock. Which one of the following best shows the path of the falling telescope as seen by Lucie?

(1)

7.	This question is about forces on charged particles.
(a)	A charged particle is situated in a field of force. Deduce the nature of the force-field (magnetic, electric or gravitational) when the force on the particle
(i)	is along the direction of the field regardless of its charge and velocity.
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(ii)	is independent of the velocity of the particle but depends on its charge.
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(iii)	depends on the velocity of the particle and its charge.
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(5)
(b)	An electron is accelerated from rest in a vacuum through a potential difference of 2.1 kV. Deduce that the final speed of the electron is 2.7 × 107 ms–1.
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(3)

	The electron in (b) then enters a region of uniform electric field between two conducting horizontal metal plates as shown below.

	The electric field outside the region of the plates may be assumed to be zero. The potential difference between the plates is 95 V and their separation is 2.2 cm.
	As the electron enters the region of the electric field, it is travelling parallel to the plates.
(c)	(i)	On the diagram above, draw an arrow at P to show the direction of the force due to the electric field acting on the electron.
(1)
(ii)	Calculate the force on the electron due to the electric field.
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(3)
(d)	The plates in the diagram opposite are of length 12 cm. Determine
(i)	the time of flight between the plates.
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(1)
(ii)	the vertical distance moved by the electron during its passage between the plates.
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(3)

(e)	Suggest why gravitational effects were not considered when calculating the deflection of the electron.
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(2)
(f)	In a mass spectrometer, electric and magnetic fields are used to select charged particles of one particular speed. A uniform magnetic field is applied in the region between the plates, such that the electron passes between the plates without being deviated.
	For this magnetic field,
(i)	state and explain its direction.
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(3)
(ii)	determine its magnitude.
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(2)
(g)	The electric and magnetic fields in (f) remain unchanged. Giving a brief explanation in each case, compare qualitatively the deflection of the electron in (f) with that of
(i)	an electron travelling at a greater initial speed.
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(ii)	a proton having the same speed.
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(iii)	an alpha particle (α-particle) having the same speed.
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(7)
(Total 30 marks)

8.	An athlete runs round a circular track at constant speed. Which one of the following graphs best represents the variation with time t of the magnitude d of the displacement of the athlete from the starting position during one lap of the track?

(1)

9.	A ball is released from rest near the surface of the Moon. Which one of the following quantities increases at a constant rate?
A.	Only distance fallen
B.	Only speed
C.	Only speed and distance fallen
D.	Only speed and acceleration
(1)

10.	A stone is thrown horizontally from the top of a high cliff. Assuming air resistance is negligible, what is the effect of gravitational force on the horizontal and on the vertical components of the velocity of the stone?
	Vertical component of velocity	Horizontal component of velocity	
A.	increases to a constant value	stays constant	
B.	increases continuously	stays constant	
C.	increases to a constant value	decreases to zero	
D.	increases continuously	decreases to zero	
(1)

11.	This question is about the kinematics of an elevator (lift).
(a)	Explain the difference between the gravitational mass and the inertial mass of an object.
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(3)
	An elevator (lift) starts from rest on the ground floor and comes to rest at a higher floor. Its motion is controlled by an electric motor. A simplified graph of the variation of the elevator’s velocity with time is shown below.

(b)	The mass of the elevator is 250 kg. Use this information to calculate
(i)	the acceleration of the elevator during the first 0.50 s.
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(2)
(ii)	the total distance travelled by the elevator.
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(2)

(iii)	the minimum work required to raise the elevator to the higher floor.
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(2)
(iv)	the minimum average power required to raise the elevator to the higher floor.
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(2)
(v)	the efficiency of the electric motor that lifts the elevator, given that the input power to the motor is 5.0 kW.
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(2)
(c)	On the graph axes below, sketch a realistic variation of velocity for the elevator. Explain your reasoning. (The simplified version is shown as a dotted line)

(2)

	The elevator is supported by a cable. The diagram below is a free-body force diagram for when the elevator is moving upwards during the first 0.50 s.

(d)	In the space below, draw free-body force diagrams for the elevator during the following time intervals.
(i)	0.5 to 11.50 s	(ii)	11.50 to 12.00 s
			
(3)
	A person is standing on weighing scales in the elevator. Before the elevator rises, the reading on the scales is W.
(e)	On the axes below, sketch a graph to show how the reading on the scales varies during the whole 12.00 s upward journey of the elevator. (Note that this is a sketch graph – you do not need to add any values.)

(3)

(f)	The elevator now returns to the ground floor where it comes to rest. Describe and explain the energy changes that take place during the whole up and down journey.
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(4)
(Total 25 marks)

12.	This question is about projectile motion and the use of an energy argument to find the speed with which a thrown stone lands in the sea.
	Christina stands close to the edge of a vertical cliff and throws a stone. The diagram below (not drawn to scale) shows part of the trajectory of the stone. Air resistance is negligible.

	Point P on the diagram is the highest point reached by the stone and point Q is at the same height above sea level as point O.

(a)	At point P on the diagram above draw arrows to represent
(i)	the acceleration of the stone (label this A).
(1)
(ii)	the velocity of the stone (label this V).
(1)
	The stone leaves Christina’s hand (point O) at a speed of 15 m s−1 in the direction shown. Her hand is at a height of 25 m above sea level. The mass of the stone is 160 g. The acceleration due to gravity g = 10 m s−2.
(b)	(i)	Calculate the kinetic energy of the stone immediately after it leaves Christina’s hand.
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(1)
(ii)	State the value of the kinetic energy at point Q.
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(1)
(iii)	Calculate the loss in potential energy of the stone in falling from point Q to hitting the sea.
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(1)
(iv)	Determine the speed with which the stone hits the sea.
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(2)
(Total 7 marks)

13.	A car is heading due East at a speed of 10 m s−1. A bird is flying due North at a speed of 4m s−1, as shown below.

	Which one of the following vectors represents the velocity of the bird relative to a person in the car?

(1)

14.	A stone is thrown from O at an angle to the horizontal. Which sketch below best shows the path of the stone when air resistance is not neglected? On each sketch, the broken line shows the path for the same stone in a vacuum.

(1)

15.	Peter and Susan both stand on the edge of a vertical cliff.

	Susan throws a stone vertically downwards and, at the same time, Peter throws a stone vertically upwards. The speed V with which both stones are thrown is the same. Neglecting air resistance, which one of the following statements is true?
A.	The stone thrown by Susan will hit the sea with a greater speed than the stone thrown by Peter.
B.	Both stones will hit the sea with the same speed no matter what the height of the cliff.
C.	In order to determine which stone hits the sea first, the height of the cliff must be known.
D.	In order to determine which stone hits the sea first both the height of the cliff and the mass of each stone must be known.
(1)

16.	A ball is dropped from rest at time t = 0 on to a horizontal surface from which it rebounds. The graph shows the variation of time t with speed v of the ball.

	Which one of the following best represents the point at which the ball just loses contact with the surface after the first bounce?
A.	A
B.	B
C.	C
D.	D
(1)

17.	Juan is standing on the platform at a railway station. A train passes through the station with speed 20 m s–1 in the direction shown measured relative to the platform. Carmen is walking along one of the carriages of the train with a speed of 2.0 m s–1 measured relative to the carriage in the direction shown. Velocity is measured as positive in the direction shown on the diagram.

	The velocity of Carmen relative to Juan is
A.	–22 m s–1.
B.	–18 m s–1.
C.	+18 m s–1.
D.	+22 m s–1.
(1)

18.	This question is about waves and wave motion.
(a)	(i)	Define what is meant by the speed of a wave.
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(2)
(ii)	Light is emitted from a candle flame. Explain why, in this situation, it is correct to refer to the “speed of the emitted light”, rather than its velocity.
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(b)	(i)	Define, by reference to wave motion, what is meant by displacement.
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(ii)	By reference to displacement, describe the difference between a longitudinal wave and a transverse wave.
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(3)
	The centre of an earthquake produces both longitudinal waves (P waves) and transverse waves (S waves). The graph below shows the variation with time t of the distance d moved by the two types of wave.

(c)	Use the graph to determine the speed of
(i)	the P waves.
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(1)
(ii)	the S waves.
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(1)
	The waves from an earthquake close to the Earth’s surface are detected at three laboratories L1, L2 and L3. The laboratories are at the corners of a triangle so that each is separated from the others by a distance of 900 km, as shown in the diagram below.

	The records of the variation with time of the vibrations produced by the earthquake as detected at the three laboratories are shown below. All three records were started at the same time.

	On each record, one pulse is made by the S wave and the other by the P wave. The separation of the two pulses is referred to as the S-P interval.
(d)	(i)	On the trace produced by laboratory L2, identify, by reference to your answers in (c), the pulse due to the P wave (label the pulse P).
(1)
(ii)	Using evidence from the records of the earthquake, state which laboratory was closest to the site of the earthquake.
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(1)

(iii)	State three separate pieces of evidence for your statement in (d)(ii).
(3)
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(iv)	The S-P intervals are 68 s, 42 s and 27 s for laboratories L1, L2 and L3 respectively. Use the graph, or otherwise, to determine the distance of the earthquake from each laboratory. Explain your working.
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Distance from L1	=	......................km
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Distance from L2	=	......................km
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Distance from L3	=	......................km
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(4)
(v)	Mark on the diagram a possible site of the earthquake.
(1)

	There is a tall building near to the site of the earthquake, as illustrated below.

	The base of the building vibrates horizontally due to the earthquake.
(e)	(i)	On the diagram above, draw the fundamental mode of vibration of the building caused by these vibrations.
(1)
	The building is of height 280 m and the mean speed of waves in the structure of the building is 3.4 × 103 ms–1.
(ii)	Explain quantitatively why earthquake waves of frequency about 6 Hz are likely to be very destructive.
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(3)
(Total 25 marks)

19.	A ball is dropped from rest at time t = 0 on to a horizontal surface from which it rebounds. Which one of the following graphs best shows the variation of speed v of the ball with time t from the time t = 0 to the time that the ball leaves the surface?

(1)

20.	Which one of the following is a true statement concerning the vertical component of the velocity and the acceleration of a projectile when it is at its maximum height? (The acceleration of free fall is g.)
	Vertical component of velocity	Acceleration	
A.	maximum	zero	
B.	maximum	g	
C.	zero	zero	
D.	zero	g	
(1)