NECO Past Questions and Answers - Page 184

916.

The most suitable instrument for measuring the diameter of a thin wire is a

A.

meter rule

B.

micrometer screw gauge

C.

pair of dividers

D.

pair of engineer’s calipers

E.

venire calipers

Correct answer is B

No explanation has been provided for this answer.

917.

When the total product starts falling, then the marginal product is

A.

Constant

B.

Increasing

C.

Maximum

D.

Negative

E.

Zero

Correct answer is D

No explanation has been provided for this answer.

919.

Which of the following statements is correct about volatile liquids? They have

A.

low boiling point

B.

Low evaporating rate

C.

high conductivity

D.

high density

E.

high viscosity

Correct answer is A

No explanation has been provided for this answer.

920.

The work done in extending a spring by 40 mm is 1.52J. Calculate the elastic constant of the spring.

A.

38.8 Nm-1

B.

60.8 Nm-1

C.

190.0 Nm-1

D.

1900.0 Nm-1

E.

3800.0 Nm-1

Correct answer is D

Force = Elastic constant x extension

Work done = \(\frac{1}{2} K \times e^2\)

Given Work done = 1.52J; Elastic constant (k) = ?; e = 40mm = 0.04 m

\(\therefore 1.52 = \frac{k \times (0.04)^2}{2}\)

\(3.04 = k \times 1.6 \times 10^{-3}\)

\(k = \frac{3.04}{1.6} \times 10^3\)

= 1.9 x 10\(^3\)

= 1900 Nm\(^{-1}\)