# 1991 - WAEC Physics Past Questions and Answers - page 1

1

Which of the following is a fundamental quantity?

A

speed

B

density

C

lenght

D

impulse

**Answer & Comments**

**correct option:**c

2

A body moves with a constant speed but has an acceleration. this process if it

A

moves in a straight line

B

moves in a circle

C

is oscillating

D

is in equilibrum

**Answer & Comments**

**correct option:**b

3

A ball is projected horizontally from the top of a hill with a velocity of 20m

^{-1}. If it reaches the ground 4 seconds later, what is the height of the hill? (g = 10ms^{-2})A

20m

B

40m

C

80m

D

160m

**Answer & Comments**

**correct option:**c

Initial horizontal velocity = 20ms

Initial vertical velocity = 0

s = ut + \(\frac{1}{2}gt^2\) = 0 x 5 x 4

= 80m

Users' Answers & Comments^{-1}Initial vertical velocity = 0

s = ut + \(\frac{1}{2}gt^2\) = 0 x 5 x 4

^{2}= 80m

4

A body moving with uniform acceleration has two points(5, 15) and (20, 60) on the velocity-times graph of its motion. Calculate

A

0.25ms

^{-2}B

3.00ms

^{-2}C

4.00ms

^{-2}D

9.00ms

^{-2}**Answer & Comments**

**correct option:**b

slope = acceleration

a = \(\frac{v_2 - v_1}{t_2 - t_1} = \frac{60- 15}{20 - 5}\)

= 3ms

Users' Answers & Commentsa = \(\frac{v_2 - v_1}{t_2 - t_1} = \frac{60- 15}{20 - 5}\)

= 3ms

^{-2}5

the diagram above shows the position of a simple pendulum set in motion. At which of the positions does the pendulum have maximum kinetic energy?

A

5

B

4

C

3

D

2

**Answer & Comments**

**correct option:**c

6

An orange fruit drops to the ground from the top of a tree 45m tall. How long does it takes to reach the ground? (g = 10ms

^{-2})A

3.0s

B

4.5s

C

6.0s

D

7.5s

**Answer & Comments**

7

power is defined as the

A

capacity to exert a force

B

product of force and time

C

product of force and distance

D

ability to do work

**Answer & Comments**

**correct option:**e

8

The product PV where P is pressure and V is volume has the same unit as

A

power

B

work

C

acceleration

D

impulse

**Answer & Comments**

9

The diagram represents a block-and-tackle pulley system on which an effort of 50N is just able to lift a load of weight W. If the efficiency of the machine is 40%. find the value of W

A

300N

B

200N

C

140N

D

120N

**Answer & Comments**

**correct option:**d

Eff = \(\frac{MA}{VR}\) x 100%

40 = \(\frac{MA}{60}\)

MA = 240

\(\frac{L}{E} = \frac{240}{100}\)

W = L = \(\frac{240}{100}\) x 50

= 120N

Users' Answers & Comments40 = \(\frac{MA}{60}\)

MA = 240

\(\frac{L}{E} = \frac{240}{100}\)

W = L = \(\frac{240}{100}\) x 50

= 120N

10

A boatman facing north wants to cross a flowing river to a point directly opposite its position at the other bank. If the river is flowing eastwards, in what direction should he row his boat?

A

west

B

east

C

north-west

D

north-east

**Answer & Comments**

**correct option:**c