JAMB Physics Past Questions & Answers - Page 25

121.

If a sound wave goes from a cold air region to a hot air region, its wavelength will?

A.

increase

B.

decrease

C.

decrease then increase

D.

remain constant

Correct answer is A

No explanation has been provided for this answer.

122.

The equation of a wave traveling along the positive x-direction is given by; y = 0.25 x 10\(^{-3}\) sin (500t - 0.025x). Determine the angular velocity of the wave motion. 

A.

0.25 x 10\(^{-3}\)rads\(^{-1}\)

B.

0.25 x 10\(^{-1}\)rads\(^{-1}\)

C.

5.00 x 10\(^{2}\)rads\(^{-1}\)

D.

2.50 x 10\(^{3}\)rads\(^{-1}\)

Correct answer is C

Using y = A sin (wt + 0)

Given y = 0.25 x 10\(^{-3}\)sin (500t - 0.025x)

By comparing, w = 5.00 x 10\(^{2}\)rads\(^{-1}\)

123.

Calculate the mass of ice that would melt when 2kg of copper is quickly transferred from boiling water to a block of ice without heat loss (specific heat capacity of copper = 400Jkg\(^{1}\)k\(^{-1}\), latent heat of fusion of ice = 3.3 x 10\(^{5}\)Jkg\(^{-1}\))

A.

\(\frac{8}{33}\)kg

B.

\(\frac{3.3}{80}\)kg

C.

\(\frac{80}{33}\)kg

D.

\(\frac{3.3}{8}\)kg

Correct answer is A

mc\(\Delta\theta\) = m\(\lambda\)f

2 x 400 (100 - 0) = m(3.3 x 10\(^{5}\))

m = \(\frac{2 \times 400 \times 100}{3.3 \times 10^{5}} = \frac{8}{33}\)kg

124.

The temperature gradient across a copper rod of thickness 0.02m, maintained at two temperature junctions of 20º and 80ºC respectively is?

A.

3.0 x 10\(^{2}\)km\(^{-1}\)

B.

3.0 x 10\(^{3}\)km\(^{-1}\)

C.

5.0 x 10\(^{3}\)km\(^{-1}\)

D.

3.0 x 10\(^{4}\)km\(^{-1}\)

Correct answer is B

\(\Delta\) = \(\frac{\bigtriangleup\theta}{\delta} = \frac{80-20}{0.02}\)

= 3.0 x 10\(^{3}\)km\(^{-1}\)

125.

I. A liquid boils when its saturated vapor pressure is equal to the external pressure
II. Dissolved substances in pure water lead to an increase in the boiling point.
III. When the external pressure is increased, the boiling point increases.
IV. Dissolved substances in pure water decreases the boiling point 

Which of the above combinations are peculiarities of the boiling point of a liquid?

A.

I, II and III only

B.

I, II, III, and IV

C.

I, II, and IV

D.

II, III, and IV

Correct answer is A

The boiling point of a liquid depends on temperature, atmospheric pressure, and the vapor pressure of the liquid.
When the atmospheric pressure is equal to the vapor pressure of the liquid, boiling will begin