1

When a ship sails from salt water into fresh water, the fraction of its volume above the water surface will

A

increase

B

decrease

C

remain the same

D

increase then decrease

CORRECT OPTION:
b

Fresh water is less dense than the salt water, hence when the ship sails in fresh water, it will sink more, thus the fraction of the ship above the water surface will decrease.

2

I. Its velocity is constant

II. No work is done on the body

III. It has constant acceleration directed away from the centre

IV. The centripetal force is directed towards the centre

Which combination of the above is true of a body moving with constant speed in a circular track?

II. No work is done on the body

III. It has constant acceleration directed away from the centre

IV. The centripetal force is directed towards the centre

Which combination of the above is true of a body moving with constant speed in a circular track?

A

II and IV

B

I and IV

C

II and III

D

I and III

CORRECT OPTION:
a

3

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

A

20N

B

30N

C

40N

D

50N

CORRECT OPTION:
c

Efficiency = M.A/V.R

75% = M.A/V.R

75/100 = M.A/5

M.A = 75(5)/100 = 3.75

But M.A = Load/Effort

3.75 = 150/Effort

Effort = 150/3.75

Effort = 40N

75% = M.A/V.R

75/100 = M.A/5

M.A = 75(5)/100 = 3.75

But M.A = Load/Effort

3.75 = 150/Effort

Effort = 150/3.75

Effort = 40N

4

At a fixed point below a liquid surface, the pressure downwards is P_{1} and pressure upwards is P_{2}. It can be deduced that

A

P_{1} > P_{2}

B

P_{1} ≥ P_{2}

C

P_{1} < P_{2}

D

P_{1} = P_{2}

CORRECT OPTION:
a

Pressure in a liquid increases with depth

5

If the force and the velocity on a system are each reduced simultaneously by half, the power of the system is

A

doubled

B

reduced to a quarter

C

reduced by half

D

constant

CORRECT OPTION:
b

6

A catapult used to hold a stone of mass 500g is extended by 20cm with an applied force F. If the stone leaves with a velocity of 40m/s, the value of F is

A

4.0 x 10^{2}N

B

2.0 x 10^{3}N

C

4.0 x 10^{3}N

D

4.0 x 10^{4}N

CORRECT OPTION:
b

Work done in extending the catapult = F(X) and this is equal to the kinetic energy imparted to the stone = 1/2MV^{2}

Thus F(X) = 1/2MV^{2}

∴ F = MV^{2}/2X

F = 0.5 x 40^{2}/2 x 0.2

F = 2000

F = 2.0 x 10^{3}N

Thus F(X) = 1/2MV

∴ F = MV

F = 0.5 x 40

F = 2000

F = 2.0 x 10

7

A stream is flowing at 0.75ms^{-1} and a boat heading perpendicular for the stream landed at the opposite bank at an angle of 30°. Calculate the velocity of the boat.

A

1.50ms^{-1}

B

1.00ms^{-1}

C

0.86ms^{-1}

D

0.65ms^{-1}

CORRECT OPTION:
c

Let the velocity of the boat = Vm/s

0.75/V = adj/hyp = Cost30°

0.75/V = 0.8660

∴ V = 0.75/0.8660

V = 0.86^{-1}

0.75/V = adj/hyp = Cost30°

0.75/V = 0.8660

∴ V = 0.75/0.8660

V = 0.86

8

A rope is being used to pull a mass of 10kg vertically upward. Determine the tension in the rope if, starting from rest, the mass acquires a velocity of 4ms^{-1} in 8s [g = 10ms^{-2}]

A

5N

B

50N

C

95N

D

105N

CORRECT OPTION:
a

9

I. The frictional force is independent of the area of the surfaces in conduct

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?

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, III and IV

B

I, II and IV

C

I, II and III

D

II, III and IV

CORRECT OPTION:
b

10

Total internal reflection occurs when light moves from

A

a dense medium to a less dense medium

B

air to water

C

water to glass

D

a less dense to a dense medium

CORRECT OPTION:
a

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