WAEC Physics Past Questions & Answers - Page 151

751.

A block and tackle system has six pulleys. a force of 50N applied to it lifts a load of weight W. If the efficiency of the system is 40%, calculate W

A.

300N

B.

200N

C.

140N

D.

120N

Correct answer is D

M.A = \(\frac{E \times V.R}{100} = \frac{40 \times 6}{100} = \frac{12}{5}\)

W = M.A x effort

= \(\frac{12}{5} \times 50 = 120N\)

752.

The velocity ratio of an inclined plane, inclines at an angle \(\theta\) to the horizontal can be expressed as

A.

(sin \(\theta)^{-1}\)

B.

\(\sin \theta\)

C.

(cos \(\theta)^{-1}\)

D.

\(\cos \theta\)

Correct answer is A

No explanation has been provided for this answer.

753.

The engine of a train produces a force of 3000N when moving at 30.ms-1. calculate the power of the engine

A.

1.00 x 102W

B.

3.00 x 104W

C.

9.00 x 104W

D.

3.00 x 105W

Correct answer is C

P = FV

= 3 x 103 x 30

= 9 x 104W

754.

The potential energy in an elastic string of force constant K which has been extended by X metres is expresses as

A.

\(\frac{1}{2}k \Box ^2\)

B.

\(k \Box ^2\)

C.

\(\frac{1}{2}k \Box \)

D.

\(k \Box \)

Correct answer is A

No explanation has been provided for this answer.

755.

Which of the following statements about the mouth piece of a telephone is correct? It converts sound energy into

A.

acoustic energy

B.

mechanical energy

C.

electrical energy

D.

heat energy

Correct answer is C

No explanation has been provided for this answer.