Physics Test

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Physics Test - 24

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Question 1
3 / -1

A rubber ball is dropped from a height of 5 m on a planet where the acceleration due to gravity is not known. On bouncing, it rises to 1.8 m. The ball loses its velocity on bouncing by a factor of

A
16/25

B
2/5

C
3/5

D
9/2

Solution
Question 2
3 / -1

Time period 'T' of a simple pendulum may depend on 'm', the mass of the bob, 'l', the length of the string, and 'g', the acceleration due to gravity. This means that 'T' ∝ m^a l^bg^c. What are the respective values of 'a', 'b' and 'c'?

A
1/2, 0 and 1/2

B
1/2, 0 and - 1/2

C
0, 1/2 and - 1/2

D
0, 1/2 and 1/2

Solution
Question 3
3 / -1

A small particle is released inside the depth of a liquid in the vessel. The volume of the particle is V. Density and viscosity of the liquid are ρ and η, respectively. Buoyant force on the particle is greater than the weight of the particle. The variation of velocity of the particle with time is

A

B

C

D

Solution

Initially the up thrust is more than its weight, so it will accelerate, i.e. its velocity increases. As the viscosity increases, the viscous force also increases. The acceleration decreases at a time when the viscous force and the weight acting downward balance the up thrust. Finally, the acceleration will become zero and it will move with a constant velocity.
Question 4
3 / -1

Which of the following quantities is unitless as well as dimensionless?

A
Angle

B
Solid angle

C
Mechanical equivalent of heat

D
Refractive index

Solution

In optics, the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as the ratio of the speed of light in vacuum relative to that in the considered medium. This can be written mathematically as:

n = speed of light in a vacuum/speed of light in a medium

Since refractive index is the ratio of same quantities, so it has no unit and is a dimensionless quantity.
Question 5
3 / -1

In the rectangular lamina ABCD shown in the figure below, a = AB = BC/2. The moment of inertia of the lamina is minimum along the axis passing through

A
BC

B
AB

C
HF

D
EG

Solution
Question 6
3 / -1

A bomber plane is moving horizontally with a speed of 600 m/s and a bomb released from it strikes the ground in 10 sec. What is the measure of angle at which the bomb strikes the ground? (g = 10 m/s²)

A
sin ^-1(1/5)

B
tan^-1 (6)

C
tan^-1(1/5)

D
tan^-1 (1/6)

Solution
Question 7
3 / -1

A spring of force constant k is cut into two equal halves. The force constant of each half is

A
k/√2

B
k/2

C
k

D
2k

Solution
Question 8
3 / -1

A body is projected at time t = 0 from a certain point on a planet’s surface with a certain velocity at a certain angle with the planet’s surface (assumed horizontal). The horizontal and vertical displacements x and y (in metres), respectively vary with time t (in seconds) as x = 10 √3 t and y = 10 t – t².

What is the value of acceleration due to the gravity on the planet’s surface?

A
1.0 ms^–2

B
2 ms^–2

C
4 ms^–2

D
9.8 ms^–2

Solution
Question 9
3 / -1

A ball, which is at rest, is dropped from a height of 'h' metres. As it bounces off the floor, its speed is 80% of what it was just before touching the ground. The ball will rise to a height of

A
0.94 h

B
0.80 h

C
0.75 h

D
0.64 h

Solution
Question 10
3 / -1

The track shown in the figure ends in a circular track of radius r with centre at O. A small solid sphere of mass m rolls from rest without slipping from a point A at a height h = 6r from the level ground. What is the speed of the sphere when it reaches a point B at height r above the level ground?

A
√(10gr)

B
√(50/7gr)

C
√(22/7gr)

D
Zero

Solution