WAEC Physics Past Questions & Answers - Page 117

581.

Which of the following instruments is best for measuring the diameter of a thin constantan wire?

A.

callipers

B.

metre rule

C.

micometer screw guage

D.

vernier callipers

Correct answer is C

No explanation has been provided for this answer.

582.

Which of the following properties of a long steel bar would alter if the bar were melted, recast into a cube and allowed to cool to its original temperature?

A.

sensity

B.

volume

C.

specific heat capacity

D.

electrical resistance

Correct answer is B

No explanation has been provided for this answer.

583.

An electron of mass 9.1 x 10-31 kg moves with a speed of 107ms-1. Calculate the wavelength of the associates wave[h = 6.6 x 10-34Js]

A.

9.0 x 10-24m

B.

4.55 x 10-17m

C.

7.25 x 10-11m

D.

6.20 x 10-8m

Correct answer is C

\(\lambda = \frac{hc}{\frac{1}{2}mv^2}\)

= \(\frac{6.6 x 10^{-34} \times 3 \times 10^8}{0.5 \times 9.1 \times 10^{-3} (10^7)^2}\)

= 7.25 x 10-11m

584.

The main difference between between x-rays and \(\gamma-rays\) lies in their

A.

ionizing ability

B.

absorption rate

C.

mode of production

D.

mode of propagation

Correct answer is D

No explanation has been provided for this answer.

585.

Two isotopes of uranium are designed as \(^{238}U\) and \(^{235}U\). The numbers 238 and 235 represent their

A.

atomic numbers

B.

nucleon numbers

C.

proton numbers

D.

neutron numbers

Correct answer is B

neutrons + protons = the nucleus or mass numbers.

U-238 has mass number(proton 92 + neutron 146=238)
U-235 has mass number (proton 92 + neutron 143 =235)