JAMB Physics Past Questions & Answers - Page 332

1,656.

A solid of weight 0.600N is totally immersed in oil and water respectively. If the upthrust of oil is 0.210N and the relative density of oil is 0.875. Find the upthrust in water.

A.

0.600N

B.

0.360N

C.

0.240N

D.

0.180N

Correct answer is C

Rd = \(\frac{\text{upthrust in oil}}{\text{upthrust in }H_2O}\)

thus; 0.875 = \(\frac{0.21}{\text{upthrust in }H_2O}\)

upthrust in H2O = 0.24N

1,657.

The atmospheric pressure due to water is 1.3 x 106Nm-2. What is the total pressure at the bottom of an ocean 10m deep? [Density of water = 1000kgm-3, g = 10ms-2]

A.

1.3 x 107Nm-2

B.

1.4 x 106Nm-2

C.

1.4 x 105Nm-2

D.

1.0 x 10 5Nm-2

Correct answer is B

Pressure = heg = 1000 x 10 x 10 = 105Nm-2

Total pressure = (1.3 x 106) + (1 x 105)

= 1.4 x 106Nm-2

1,659.

The tendon in a man's leg is 0.01m long. If a force of 5N stretches the tendon by 2.0 x 10-5m, calculate the strain on the muscle.

A.

5 x 106

B.

5 x 102

C.

2 x 10-3

D.

2 x 10-7

Correct answer is C

Strain = \(\frac{extension}{\text{original length}}\)

\(\frac{2 {\times} 10^{-5}}{0.01}\)

= 2 x 10-3

1,660.

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

A.

20N

B.

25N

C.

50N

D.

80N

Correct answer is B

Efficiency = \(\frac{\text{work done by hand}}{\text{work done by effort}}\)

80 = \(\frac{100{\times 8}}{E {\times} 40}\) x \(\frac{100}{1}\)

E = 25N