Work, Energy, Power and Friction Generix Content - Work, Energy, Power and Friction
"Work, Energy, Power and Friction" question number distribution across years
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JAMB questions for "Physics :: Work, Energy, Power and Friction"
Q1
A boy drags a bag of rice along a smooth horizontal floor with a force of 2N applied at an angle of 60° to the floor. The work done after a distance of 3m is
A
6J
B
3J
C
4J
D
5J
E
Q2
The figure beside shows 4 forces 3N, 10N, 3&#8730;3N and 6N acting on a particle P. The resultant of the four forces is
A
10N
B
10&#8730;3N
C
5N
D
5&#8730;3N
E
Q3

The correct unit of energy density is

A

kg m-1s-2

B

kg m-3s-2

C

kg m2s-2

D

kg m3s-2

E
Q4

An engine of a car of power 80 kW moves on a rough road with a velocity of 32 ms-1 . The force required to bring it to rest is

A

2.50 X 106N

B

2.56 X 106N

C

2.50 X 103N

D

2.80 X 103N

E
Q5

The amount of energy released when 0.5kg of uranium is burnt completely is

A

4.5 X 1016J

B

1.5 X 1016J

C

1.5 X 108J

D

4.5 X 108J

E
Q6
A force of 200 n acts between two objects at a certain distance apart. The value of the force when the distance is halved is
A
100 N
B
200 N
C
800 N
D
400 N
E
Q7
In the figure below, the work done by the force of 100N inclined at an angle of 600 to the object dragged horizontally to a distance of 8m is
A
600J
B
800J
C
400J
D
100J
E
Q8
A steady current of 2A flows in a coil of emf 12V for 0.4s. A back emf of 3V was induced during this period. The stored energy in the loop that can be utilized is
A
9.6 J
B
2.4 J
C
12.0 J
D
7.2 J
E
Q9

In a hydraulic press, a force of 40N is applied on the effort piston of area 0.4m2.  If the force exerted on the load piston is 400N, the area of the large piston is

A

4m2

B

8m2

C

2m2

D

1m2

E
Q10

A 100kg box is pushed along a road with a force of 500N. If the box moves with a uniform velocity, the coefficient of friction between the box and the road is

A

0.4

B

1.0

C

0.8

D

0.5

E
Q11

A man exerts a pressure of 2.8 X 103Nm-2 on the ground and has 4 x 10-2m-2 of his feet in contact with the ground . The weight of the man is

A

102 N

B

70 N

C

140 N

D

112 N

E
Q12
The diagram below shows forces 4N, 6N, 10N and 8N which act at a point O in the directions indicated. The net horizontal force is
A
13N
B
17N
C
&#8730;3N
D
7&#8730;3N
E
Q13
If an object just begins to slide on a surface inclined at 30° to the horizontal, the coefficient of friction is
A
1/&#8730;3
B
1/&#8730;2
C
&#8730;3
D
3/&#8730;2
E
Q14

A bead travelling  on a straight ire is brought to rest at 0.2m by friction. If the mass of the bead is 0.01 kg and the coefficient of friction between the bead and wire is 0.1, determine the work done by the friction

A

2 x 10-3 J

B

2 x 102J

C

2 x 10-4 J

D

2 x 101J

E
Q15

The stylus of a photograph record exerts a force of 7.7 x 10-2 N on a groove of radius 10-5m, Compute the pressure exerted by the stylus on the groove

A

2.42 x 109 Nm-2

B

4.90 x 108 Nm-2

C

2.45 x 108Nm-2

D

3.45 x 108 Nm-2

E
Q16
I. The earth is not spherical but elliptical in shape  II. Variation in latitude and longitude III. Rotation of the earth on its axis  IV. Variation in the density of the earth  On which combination of the above does the weight of an object vary on the earth's surface?
A
I and II only
B
I, II and III only
C
II, III and IV only
D
I, II, III  and IV
E
Q17
I. The frictional force is independent of the area of the surfaces in contact II. The frictional force depends on the nature  of the surfaces in contact  III. The frictional force depends on the speed of sliding  IV. The frictional force is directly proportional to the normal reaction. Which combination of the above is true of sliding friction?
A
I, II and IV
B
I, II and III
C
I , II and IV
D
II, III and IV
E
Q18

A ball of mass 0.1 kg is thrown vertically upwards with a speed of 10 ms-1 from the top of a tower 10m high. Neglecting all resistance, its total energy just before hitting the ground is

A

5 J

B

10 J

C

15 J

D

20 J

E
Q19

A car of mass 300 kg attains a speed of 25 ms-1 in 20 seconds. The power developed in the engine is

A

1.25 x 104 W

B

2.50 x 104 W

C

1.25 X 106 W

D

2.50 X 106 W

E
Q20
When the brakes in a car are applied, the frictional force on the tyres is
A
a disavantage because it is in the direction of motion of the car
B
disadvantage because it is in the opposite direction of motion of the car
C
an advantage because it is in the direction of motion of the car
D
an advantage because it is in the opposite direction of motion of the car
E
Q21
The diagram beside shows a solid figure with base PQ and centre of gravity G on an inclined plane. Which of the following statements is correct?
A
The solid will fall over if the vertical line through G lies outside the base
B
the solid will fall over if the vertical line through G lies inside the base
C
the solid will not fall over if the vertical line through G lies outside the base
D
the solid can never fall over
E
Q22

A man whose mass is 80 kg climbs a staircase in 20 s and expends a power of 120 W. Find the height of the staircase

A

1.8 m

B

2.0 m

C

2.5 m

D

3.0 m

E
Q23
A parachute attains a terminal velocity when
A
its density is equal to the density of air
B
the viscous force of the air and the upthrust completely counteract its weight
C
it expands as a result of reduced external pressure
D
the viscous force of the air is equal to the sum of the weight and upthrust
E
Q24

A 5 kg block is released from rest on a smooth plane inclined at an angle of 30° to the horizontal. What is its acceleration down the plane?

A

5.0 ms-2

B

5.8 ms-2

C

8.7 ms-2

D

25.0 ms-2

E
Q25

An object of mass 100 g projected vertically upwards from the ground level has a velocity of 20 ms-1 at height of 10 m. Calculate its initial kinetic energy at the ground level.

A

10 J

B

20 J

C

30 J

D

50 J

E
Q26
The figure beside shows a block of mass, m, sliding down a rough inclined plane QP at angle &#952;. The forces acting on the block along the plane QP are
A
mg sin &#952; and the normal reaction
B
mg sin &#952; and the force of friction
C
mg cos &#952; and the normal reaction
D
mg cos &#952; and the force of friction
E
Q27
For a rough inclined plane on which lies a body of weight W, the angle &#952; in the diagram above becomes the angle of friction if
A
tan &#952; = coefficient of static friction
B
cos &#952; = coefficient of dynamic friction
C
sin &#952; = coefficient of sliding friction
D
sec &#952; = limiting frictonal force
E
Q28
Which of the following statements are TRUE about  frictional force?  I. It is always a disadvantage  II. It is sometimes a disadvantage III. It always exists where there is a relative motion of two bodies that are in contact IV. It is sometimes very useful
A
I and III only
B
I and IV only
C
II and III only
D
II and IV only
E
Q29
The energy contained in a wire when it is extended by 0.02 m by a force of 500 N is
A
5 J
B
10 J
C
103  J
D
104 J
E
Q30
A hydraulic press has a large circular piston of radius 0.8 m and a circular piston of radius 0.8 m and a circular plunger of radius 0.2 m. A force of 500 N is exerted by the plunger. Find the force exerted on the piston .
A
8 000 N
B
4 000 N
C
2 000 N
D
31 N
E
Q31
A box of mass 40 kg is being dragged along the floor by a rope inclined at 600 to the horizontal. The frictional force between the box and the floor is 100N and the tension on the rope is 300N. How much work is done in dragging the box through a distance of 4 m?
A
680 J
B
400 J
C
200 J
D
100 J
E
Q32
A cone in an unstable equilibrium has its potential energy
A
decreased
B
increased
C
unchanged
D
oscillating
E
Q33

Calculate the magnitude of the force required to just move a 20 kg object along a horizontal surface if the coefficient of friction is 0.2 [g= 10ms-2]

A

400.0 N

B

40.0 N

C

4.0 N

D

0.4 N

E
Q34
Which of the following correctly describes the energy changes in the generation of light by a hydroelectric power station?
A
Electrical---->mechanical ----> potential ----> light
B
Potential ----> mechanical ----> electrical ----> light
C
Mechanical ----> sound ---->electrical ----> light
D
Kinetic ----> mechanical ----> electrical ----> light
E
Q35

In the diagram below, the hanging mass m2, is adjusted until m1 is on the verge of sliding. The coefficient of static friction between the mass m1 and the table is

A

m1/m2

B

m1g/m2

C

m2/m1

D

m2g/m1

E
Q36

A spring of force constant  1500 Nm-1 , acted upon by a constant force of 75N. Calculate the potential energy stored in the spring.

A

1.9 J

B

3.2 J

C

3.8 J

D

5.0 J

E
Q37
A body is under the action of a force such that the force displacement graph of the body is semi circular as shown below. The work done on the body by the force in moving through 24 metres is
A
36 &#960; J
B
72 &#960; J
C
144 &#960; J
D
288 &#960; J
E
Q38
To keep a vehicle moving at a constant speed v, requires power P, from the engine . The force provided by the engine is
A
p/v
B
1/2 v
C
pv
D
p/v2
E
Q39
A stone of mass m kg is held h meters above the floor for 50s. The work done in joules over this period is
A
mh
B
mgh
C
mgh/50
D
0
E
Q40
A body of mass 10kg rests on a rough inclined plane whose angle of tilt &#952; is variable . &#952; is gradually increased until the body starts to slide down the plane at 30°. The coefficient of limiting friction between the body and the plane is
A
0.30
B
0.50
C
0.58
D
0.87
E
Q41
A block-and-tackle system is used to lift a load of 20N through a vertical height of 10 m. If the efficiency of the system is 40%, how much work is done against friction?
A
80J
B
120J
C
300 J
D
500 J
E
Q42

A simple pendulum of mass m moves along an arc of a circle radius R in a vertical plane as shown in the figure above. What is the work done by gravity in a downward swing through the angle θ to 0°

A

mgR sinθ

B

mgR (1-cosθ)

C

mgR

D

mgR (1- sinθ)

E
Q43
A block of mass m is held in equilibrium against a vertical wall by a horizontal force. If the coefficient of friction between the block and the wall is u, the minimum value of the horizontal force is
A
u mg
B
(I - u) mg
C
(I + u) mg
D
mg/u
E
Q44
How long will it take a 60kg man to climb a height of 22m if he expended energy at the rate of 0.25 K W?
A
5.3s
B
34.5s
C
41.6s
D
52.8s
E
Q45

A force 10N , drags a mass 10kg on a horizontal table with an acceleration of 0.2 ms-2 . If the acceleration due to gravity is 10m-2 , the coefficient of friction between the moving mass and the table is

A

0.02

B

0.08

C

0.20

D

0.80

E
Q46
A dynamo primarily converts
A
mechanical energy into electrical energy
B
electrical energy into mechanical energy
C
Potential energy into kinetic energy
D
kinetic energy into potential energy
E
Q47

A constant force of 40N acting on a body initially at rest gives ab acceleration of 0.1 ms-1 for 4s. Calculate work done by the force

A

8J

B

10 J

C

32 J

D

160 J

E
Q48

A body rolls down a slope from a height of 100m. Its velocity at the foot of the slope is 20ms-1 . What percentage of its initial potential energy is converted kinetic energy?

A

40%

B

35%

C

20%

D

15%

E
Q49

The coefficient of static friction between a 40kg crate and a concrete surface is 0.25. Find the magnitude of the minimum force needed to keep the crate stationary on the concrete base inclined at 45° to the horizontal

A

400 N

B

300 N

C

283 N

D

212 N

E
Q50
The mechanical advantage (MA) of an inclined plane depends on
A
its length
B
its height
C
the product of its length and height
D
the ratio of its length to its height
E
Q51

Figure 3 below represents the main sequence of energy conversion at Kainji dam. The efficiency of the system is

A

Q1/Q2

B

E/Q1

C

E/(Q1-Q2)

D

E/(Q1+Q2)

E
Q52

When a box of mass 45 kg is given an initial speed of 5 m s-1, it slides along a horizontal floor a distance of 3 m before coming to rest. What is the coefficient of the kinetic friction between the box and the floor ? ( g = 10 m s-2)

A

5/6

B

5/12

C

1/3

D

2/3

E
Q53
A metal block of mass 5 kg lies on a rough horizontal platform . If a horizontal force of 8 N applied to the block through its centre of mass just slides the block on the platform, then the coefficient of limiting friction between the block and the platform is
A
0.16
B
0.63
C
0.80
D
1.60
E
2.00
Q54
If a water pump at Kainji Dam is capable of lifting 1000 kg of water through a vertical height of 10 m in 10 s, the power of the pump is
A
1.0 kW
B
10.0 kW
C
12.5 kW
D
15.0 kW
E
20.0kW
Q55
A device that converts sound energy into electrical energy is
A
the horn of a motor car
B
an A.C generator
C
a microphone
D
the telephone ear-piece
E
a loudspeaker
Q56
Which of the following statements about friction is NOT correct?
A
The force of kinectic friction is less than the force of static friction
B
The force of kinetic friction between two surfaces is independent of the areas in contact provided the normal reaction is unchanged
C
The force of rolling friction between two surfaces is less than the force of sliding friction
D
The angle of friction is the angle between the normal reaction and the force of friction
E
Friction may be reduced by lubrication
Q57
A force of 16N is applied to a 4.0 kg block that is at rest on a smooth , horizontal surface . What is the velocity of the block at t=5 seconds ?
A
4 m/s
B
10 m/s
C
20 m/s
D
50 m/s
E
80 m/s
Q58
Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?
A
Heat&#8594; Light &#8594; Sound &#8594; Kinetic
B
Kinetic&#8594; LIght &#8594; Heat &#8594; Electricity
C
Heat &#8594; Kinetic &#8594; Electricity &#8594; Heat and Light
D
Electricity &#8594; Kinetic &#8594; Heat &#8594;Light
E
Heat &#8594; Sound &#8594; KInetic &#8594; Electricity
Q59
A brick at rest on a horizontal table is pulled by a horizontal cord, as shown in Fig. 2. The force of friction on the brick.
A
increases if the pull increases but the brick does not move
B
is directly horizontal to the right
C
decreases if an identical brick is placed on the first
D
is zero if the brick is pulled hard enough to make it slide
E
changes if the brick is turned on its side
Q60

In the given diagram (Fig 11), the values of the vertically suspended weight W and the angle X are

A

2 kgf, 30.9°

B

4 kgf, 36.9°

C

6 kgf, 53.81°

D

8 kgf, 73.8°

E

12 kgf, 106.2°