Physics Questions & Answers - Free Online Practice

4,111.

A particle in circular motion performs 30 oscillation in 6 seconds. Its angular velocity is

5 rad s^-1

6 rad s^-1

5π rad s^-1

10π rad s^-1

Correct answer is D

Angular velocity w = 2π f.
But f = frequency no. of oscillations per second.
= 30/6 = 5Hz.
therefore W = 2π x 5
= 10π rad. s^-1

4,112.

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

4,113.

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

4,114.

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.

4,115.

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