"Simple Machines" question number distribution across years

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Physics index on skoool nigeria

JAMB questions for "Physics :: Simple Machines"

Q1

A machine has a velocity ratio of 4. If it requires 800N to overcome a load of 1600N, what is the efficiency of the machine?

A

2%

B

40%

C

60%

D

50%

E

**Answer:** D

Q2

A particle of weight 120N is placed on a plane inclined at an angle 30° to the horizontal. If the plane has an efficiency of 60%, what is the force required to push the weight uniformity up the plane?

A

175N

B

50N

C

210N

D

100N

E

**Answer:** D

Q3

In the diagram above, a rod 50cm long of uniform cross-section is suspended horizontally on a fulcrum, F, by the action of two forces. What is the weight of the rod?

A

200N

B

120N

C

80N

D

40N

E

**Answer:** C

Q4

I. Work done by a load is always less than the work done by effort
II. All machines are made of levers, pulleys, screws and gear wheels
III. A fishing rod is a machine
IV. Effort is always larger than load
Which of the statements above about machines are true?

A

II and III

B

I and II

C

III and IV

D

I and III

E

**Answer:** D

Q5

A mirror of weight 75 N is hung by a cord from a hook on the wall . If the cord makes an angle of 30° with the horizontal, the tension in the cord is

A

100 N

B

150 N

C

1500 N

D

250 N

E

**Answer:** B

Q6

In an ideal wheel and axle system, R stands for radius of the wheel and r is the radius of the axle. The mechanical advantage is

A

R/r

B

(r/R)^{2}

C

r/R

D

(R/r)^{2}

E

**Answer:** A

Q7

A machine whose efficiency is 60% has a velocity ratio of 5. If a force of 500N is applied to lift a load P, what is the magnitude of P?

A

1500 N

B

500 N

C

4166 N

D

750 N

E

**Answer:** A

Q8

A 90cm uniform lever has a load of 30N suspended at 15cm from one of its end. If the fulcrum is at the centre of gravity, the force that must be applied at its other end to keep it in horizontal equilibrium is

A

20 N

B

30 N

C

60 N

D

15 N

E

**Answer:** A

Q9

A wheel and axle is used to raise a load of 500 N by the application of an effort of 250 N. If the radii of the wheel and the axle are 0.4cm and 0.1 cm respectively, the efficiency of the machine is

A

60%

B

50%

C

40%

D

20%

E

**Answer:** B

Q10

The efficiency of a machine is always less than 100% because the

A

load lifted is always greater than the effort applied

B

effort applied is always greater than the load lifted

C

velocity ratio is always greater the the mechanical advantage

D

work output is always greater than the work input

E

**Answer:** C

Q11

The diagram below is a block-and-tackle pulley system in which an effort of 80N is used to lift a load of 240N. The efficiency of the machine is

A

33%

B

40%

C

50%

D

60%

E

**Answer:** C

Q12

The velocity ratio is 5 and its efficiency is 75%. What effort would be needed to lift a load of 150 N with the machine ?

A

50 N

B

40 N

C

30 N

D

20 N

E

**Answer:** B

Q13

The diagram below shows a lift pump with valves at P and Q. During a downward stroke of the piston,

A

both valves are open

B

P is open while Q is closed

C

P is closed while Q is open

D

both valves are closed

E

**Answer:** B

Q14

The figure below represents a frictionless pullery system in which a weight W is in equilibrium with a weight of 40N. Find the value of W.

A

13.3N

B

20.0N

C

40.0N

D

80.0N

E

**Answer:** D

Q15

A uniform meter rule weighing 0.5 N is to be pivoted on a knife-edge at the 30cm -mark. Where will a force of 2 N be placed from the pivot to balance the meter rule?

A

95 cm

B

25 cm

C

20 cm

D

5 cm

E

**Answer:** B

Q16

In a wheel and axle are 40 cm and 8 cm respectively . Given that the machine is 80% efficient. What effort is required to lift a load of 100 N ?

A

20 N

B

25 N

C

50 N

D

80 N

E

**Answer:** B

Q17

An electric water pump rated 1.5kW, lifts 200 kg of water through a vertical height of 6 metres in 10 seconds. What is the efficiency of the pump?

A

90.0 %

B

85.0%

C

80.0%

D

65.0%

E

**Answer:** C

Q19

A uniform rod PQ of length 1 m and mass 2 kg is pivoted at the end P. If a load of 14 N is placed at the centre of the rod , find the force that should be applied vertically upwards at Q to maintain the rod in equilibrium horizontally

A

68 N

B

28 N

C

17 N

D

7 N

E

**Answer:** C

Q20

Which of the following levers has the greatest mechanical advantage?

A

B

C

D

E

**Answer:** C

Q21

Which of the following graphs correctly represents the relationship between the load the velocity ratio of a machine?

A

B

C

D

E

**Answer:** B

Q22

The diagram below shows a uniform wood of weight 200N and length 50m. It is provided at one end and suspended by a cord at the other end at an angle of 300 to the wood. Calculate the tension in the cord if the wood is horizontal.

A

10N

B

20N

C

100N

D

200N

E

**Answer:** C

Q23

In the diagram below, a lever of length 200m is used to lift a load of mass 180kg. The pivot at P is 20m from the load. What minimum force, F, must be applied at the end of the lever? [g = 10 ms^{-2}]

A

9N

B

18N

C

20N

D

200N

E

**Answer:** D

Q24

A machine requires 1000 J of work to raise a load of 500 N through a vertical distance of 1.5 m. Calculate the efficiency of the machine

A

80%

B

75%

C

50%

D

33%

E

**Answer:** B

Q25

A wheel and axle have radii 80cm and 10 cm respectively. If the efficiency of the machine is 0.85, an applied force of 1200 N to the wheel will raise a load of

A

8. 0N

B

6.8 N

C

8160 N

D

9600.0 N

E

**Answer:** C

Q26

A 20kg mass is to be pulled up a slope inclined at 30° to the horizontal. If the efficiency of the plane is 75%, the force required to pull the load up the plane is

A

13.3 N

B

73.5N

C

133.3 N

D

533.2 N

E

**Answer:** C

Q27

A 20-toothed gear wheel drives a 60-toothed one. If the angular speed of the smaller wheel is 120revs^{-1} , the angular speed off the larger wheel is

A

3 revs^{ -1}

B

40 revs ^{-1}

C

360 revs ^{-1}

D

2400 revs^{-1}

E

**Answer:** C

Q28

Which of the following graphs correctly describes the variation of the mechanical advantage with load for a simple machine whose velocity ratio is 3?

A

B

C

D

E

**Answer:** A

Q29

Fig 4 represents a block-and-tackle pulley system on which an effort of W Newtons supports a load of 120.0N. If the efficiency of the machine is 40%, then the value of W is

A

28.0 N

B

48.0 N

C

50.0 N

D

288.0 N

E

**Answer:** C

Q30

A plane inclined at an angle of 30° to the horizontal has an efficiency of 60% . The force parallel to the plane required to push a load of 120N uniformly up the plane is

A

60 N

B

100 N

C

120 N

D

200 N

E

240 N

**Answer:** B

Q31

A machine has a velocity ratio of 5. It requires a 50 kg weight to overcome a 200 kg weight . The efficiency is

A

4%

B

5%

C

40%

D

50%

E

80%

**Answer:** E

Q32

Which of the following machines does NOT apply the lever principles?

A

Claw hammer

B

Wheel barrow

C

Single moving pulley

D

Sugar tongs

E

Nutcrackers

**Answer:** C

Q33

A uniform beam PQ if mass 20kg and length 5m is balanced as shown (Fig 8). A man of weight 800N stands at M such that QM = 2m. The reaction at P and Q respectively are (take g = 10m s^{-2})

A

300 N and 500 N

B

420 N and 580 N

C

220 N and 380 N

D

580 N and 420 N

E

380 N and 220 N

**Answer:** B

Q34

A body of mass 10kg on a smooth inclined plane is connected over a smooth pulley to a mass of 15kg as shown (Fig 13). The acceleration of the system is

A

1/4 g

B

8/25 g

C

1/2 g

D

g

E

3/4 g

**Answer:** D

Q35

An inclined plane of angle θ, acting as a simple machine, has a velocity ratio

A

sin θ

B

1/sinθ

C

cos θ

D

1/cos θ

E

sin θ cos θ

**Answer:** B

Q36

A mass of 2kg on a surface (u = 1/2) is connected to a second mass of 4kg over a frictionless pulley as shown in Fig 4. If the acceleration due to gravity is 9.8ms^{-2} then the masses will

A

accelerate at 4.9 ms^{-2}

B

remain stationary

C

accelerate at 9.8 ms^{-2}

D

accelerate at 19.6 ms^{-2}

E

accelerate at 39.2 ms^{-2}

**Answer:** A

Q37

Which of the following statements defines correctly the efficiency of a mahine ?

A

The load carried by the machine divded by effort required in carrying the load

B

The distance moved by the load divided by the distance moved by the effort

C

The useful work done by the machine divided by the total work put into it

D

The movement of the load divided by the movement of the effort about the same point

E

The temperature at the end of the application of the machine divided by the initial temperature

**Answer:** C

Q38

A weight of 1000 grams hangs from a lever 20 cm to the right of the fulcrum. At the left is a 500-gram weight 20 cm from the fulcrum, and 200-gram weight x cm away from the fulcrum. What is the value of x that will make the lever balanced?

A

50 cm

B

20 cm

C

10 cm

D

30 cm

E

70 cm

**Answer:** A

Q39

Fig 10 shows a see-saw which is exactly in balance. The weights of the people sitting on it are 50kg, Xkg and 15kg as shwon. They sit at distances of 1 1/2 m, 1 1/2 m, and 2m from the pivot respectively. The value of x is

A

30

B

35

C

70

D

26 1/4

E

impossible to find

**Answer:** A