JAMB Physics Past Questions & Answers - Page 191

951.

Consider a thick glass tumbler and a thin glass tumbler which are made of the same kind of glass. Some hot liquid is poured into them. Which of the following statements is correct?

A.

the thick tumbler is less likely to crack because it is stronger

B.

the thick tumbler is less likely to crack because it insulates the heat better, glass being a poor conductor of heat

C.

Both tumblers are equally likely to crack because they are made of the same kind of glass

D.

the thick tumbler is more likely to crack because uneven expansion persists for a longer time within the thicker glass

E.

the thick tumbler is more likely to crack because it is heavier

Correct answer is D

Usually,  when pour water into a glass, the more thick glass is easier to break. Because the glass tumbler is cold, when hot water is poured, and the inner wall expands rapidly due to thermal expansion and contraction.

953.
954.

The bulb of a motorcycle head-lamp is marked 40W, 6V. The resistance of the filament when it is switched on is

A.

\(\frac{6^2}{40^2}\)ohms

B.

\(\frac{40}{6^2}\)ohms

C.

\(\frac{40}{6}\)ohms

D.

6 x 40 ohms

E.

\(\frac{6^2}{40}\)ohms

Correct answer is E

Power \(\frac{V^2}{R}\)

40 = \(\frac{6 \times 6}{r}\)

R = \(\frac{36}{40}\)\(\Omega\)

955.

Which of the following is the correct definition of 'half-life'?

A.

the average life-time of a radioactive material

B.

the time it takes a radioactive material to decay to half of its original quantity

C.

half the period a radioactive material decays completely

D.

half of the decay constant

E.

the decay constant times life-time

Correct answer is B

No explanation has been provided for this answer.