JAMB Physics Past Questions & Answers - Page 445

2,221.

Two force each of 10N acts on a body, one towards the north and the other towards the east.
The magnitude and the direction of the resultant force are

20N, 45°E

20N, 45°W

10√2N, 45°W

10√2N, 45°E

View answer & explanation

Correct answer is D

From Pythagoras,
R2 = 10^{2 + 102}
= 100 + 100
= 200
therefore R2 = √200 = √2 x 100
= 10√2, in the direction 45°E

2,222.

If the distance between two suspended masses 10kg each is tripled, the gravitational force of attraction between them is reduced by

one half

one third

one quarter

one ninth

View answer & explanation

Correct answer is D

Let the distance apart the two masses = m.
From the equation F & M₁ m₂/ϒ²
F₁ α 10 x 10/ϒ² = F α 100/ ϒ²
F² α 10 X 10/(3ϒ)² => F² α 100/9ϒ²
therefore F²/F¹ = 100/9ϒ²/100/ϒ² = 100/9ϒ² ϒ²/100 = 1/9
Therefore F ₂ : F ₁ = 1 : 9

2,223.

A body weighing 80N stands in an elevator that is about to move. The force exerted by floor on the body as the elevator moves upward with an acceleration of 5 ms-2 is
[g = 10ms-2]

40 N

80 N

120 N

160 N

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

2,224.

The hydrostatic blood pressure difference between the head and the feet of a boy standing straight is 1.65 x 104 Nm-2. Find the height of the boy.

[ Density of blood = 1.1 x 103 kgm-3, g = 10ms-2]

0.5 m

0.6 m

1.5 m

2.0 m

View answer & explanation

Correct answer is C

[ Density of blood = 1.1 x 103 kgm-3, g = 10ms-2]
Pressure = pgh, where p = density, h = the height, g = acceleration of free fall due to gravity
1.6.5 x 104 = 1.1 x 103 x 10 x h
therefore h = 1.65 x 104/1.1 x 103 x 10 = 1.5m

2,225.

A wheel and axle is used to raise a load of 500 N by the application of an effort of 250 N. If the radii of the wheel and the axle are 0.4 cm and 0.1 cm respectively, the efficiency of the machine is

20 %

40 %

50 %

60 %

View answer & explanation

Correct answer is C

Efficiency = M.A/V.R X 100/1 M.A = Load/Effort = 500/250
= 2
V.R. = radius of wheel/radius of axle = 0.4/0.1 = 4.
therefore Efficiency = 2/4 x 100/1 = 50 %