JAMB Physics Past Questions & Answers - Page 26

126.

A piece of substance of specific heat capacity 450Jkg\(^{-1}\)k\(^{1}\) falls through a vertical distance of 20m from rest. Calculate the rise in temperature of the substance on hitting the ground when all its energies are converted into heat. [g = 10ms\(^{-2}\)]

 

A.

\(\frac{2}{9}\)ºC

B.

\(\frac{4}{9}\)ºC

C.

\(\frac{9}{2}\)ºC

D.

\(\frac{9}{4}\)ºC

Correct answer is B

Using the law of conservation of energy

mc\(\bigtriangleup\theta\) = mgh

\(\bigtriangleup\theta\) = \(\frac{gh}{c} = \frac{10 \times 20}{450} = \frac{4}{9}\)ºC

127.

A gas at a volume of V\(_{0}\) in a container at pressure p\(_{0}\) is compressed to one-fifth of its volume. What will be its pressure if the magnitude of its original temperature T is constant?

A.

\(\frac{p_{0}} {5}\)

B.

\(\frac{4p_{0}}{5}\)

C.

p\(_{0}\)

D.

5P\(_{0}\)

Correct answer is D

p\(_{1}\) = P\(_{0}\), V\(_{1}\) = V\(_{0}\), V\(_{2}\) = \(\frac{1}{5}\)V\(_{0}\) P\(_{2}\) = ?

P\(_{1}\)V\(_{1}\) = P\(_{2}\)V\(_{2}\)

P\(_{2}\) = \(\frac{P_{1}V_{1}}{V_{1}}\)

= \(\frac{\not P_{o}V_{o}}{\frac{1}{5}P_{o}}\) = 5\(\not P_{o}\)

128.

When the temperature of a liquid increases, its surface tension

A.

decreases

B.

increases

C.

remains constant

D.

increases then decreases

Correct answer is A

Surface tension decreases by:

* Increasing liquid's temperature

* Adding soap to the liquid

129.

A solid weighs 10.00N in air, 6N when forcefully immersed in water, and 7.0N when fully immersed in a liquid, X. Calculate the relative density of the liquid X.

A.

\(\frac{5}{3}\)

B.

\(\frac{4}{3}\)

C.

\(\frac{3}{4}\)

D.

\(\frac{7}{10}\)

Correct answer is C

R.D = \(\frac{\text {weigh in air - weigh in liquid X}}{\text {weigh in air - weigh in water}}\)

= \(\frac{10 - 7}{10 - 6} = \frac{3}{4}\)

130.

If the stress on a wire is 10\(^{7}\)NM\(^{-2}\) and the wire is stretched from its original length of 10.00m to 10.05m. The young's modulus of the wire is?

A.

5.0 x 10\(^{-4}\)Nm\(^{-2}\)

B.

5.0 x 10\(^{-5}\)Nm\(^{-2}\)

C.

2.0 x 10\(^{-8}\)Nm\(^{-2}\)

D.

2.0 x 10\(^{9}\)Nm\(^{-2}\)

Correct answer is D

Young's modulus \(\frac{stress}{strain}\)

Strain = \(\frac{e}{l} = \frac{0.05}{10} = \frac{10^{7}}{0.005}\)

2 x 10\(^{9}\)Nm\(^{-2}\)