JAMB Physics Past Questions & Answers - Page 385

1,921.

A plastic sphere floats in water with 50% of its volume submerged. if it floats in glycerine with 40% of its volume submerged,the density of the glycerine is?

A.

1400 kgm-3

B.

1250 kgm-3

C.

500 kgm-3

D.

1000 kgm-3

Correct answer is B

Weight of glycerine displaced = weight of water dispalced
Mgh glycerine = Mgh water
Pvgh glycerine = Pvgh water
0.4V P glycerine = (0.5v)/v.4v P water = 1.25
(Polycerine)/p water =
But density of substance = relative density x density of water = 1. 25 x 1000kgm3 = 1250kgm-3

1,922.

If a load of mass 10N stretched a cord by 1.2cm, what is the total work done?

A.

6.0 x 10-2J

B.

7.6 x 10-2J

C.

1.8 x 10-2J

D.

6.6 x 10-2J

Correct answer is A

Work done on a stretched cord
= Average force x extension
= \(\frac{1 \times 10 \times 0.012}{2}\)
= 6.0 x 10\(^{-2}\)J

1,923.

I. Density of the liquid.
II. Acceleration due to gravity.
III. Type of container of the liquid.
IV. The constituents of the liquid.

Which of the above conditions will NOT affect the pressure of fluid?

A.

I and III only

B.

II and III only

C.

III and IV only

D.

I and II only

Correct answer is C

pressure in fluid is given by P = hpg.
∴ fluid pressure depends on height of liquid column, h, density of liquid p and acceleration of free fall g. it is therefore independent of type of container and constituents of the liquid.

1,924.

If a heavy barrel is rolled up a plane inclined at 30° to the horizontal. its velocity ratio will be?

A.

3.0

B.

3.1

C.

3.2

D.

2.0

Correct answer is D

V.R = \(\frac{1}{sinθ}\)

= \(\frac{1}{sin 30°}\)

= \(\frac{1}{0.5}\)

= 2

1,925.

An object of mass 80 kg is pulled on a horizontal rough ground by a force of 500 N. Find the coefficient of static friction.
[g = 10 ms-2]

A.

0.8

B.

0.4

C.

1.0

D.

0.6

Correct answer is D

coefficient of friction

= \(\frac{F}{R}\)

=\(\frac{F}{mg}\)

 = \(\frac{500}{80 \times 10}\)
= 0.625