## What is the stress known as when there is a relative displacement between various layers of solid?

A. Tangential
B. Linear
C. Lateral
D. Longitudinal

When successive layers of solid move on each other i.e. when there is a relative displacement between various layers of solid, the stress produced is called as Tangential stress.

## By how much the orbital velocity of Moon has to increase for it to cease to remain the earth’s satellite?

A. 2 times
B. 3 times
C. √2 times
D. √3 times

If the speed of a satellite orbiting close to the earth is made √2 times (or increased by 41%) then it will escape from the gravitational field. Moon is a natural satellite of the earth.

## What is the orbital velocity of a satellite orbiting very close to the surface of earth?

A. 7.92 km/s
B. 9.8 km/s
C. 11.2 km/s
D. 14.8 km/s

In this case, the radius of the orbit will be nearly equal to the radius of earth. The orbital velocity of a satellite orbiting very close to the surface of earth is 7.92 km/s.

## The value of acceleration due to gravity is minimum on which of these planets?

A. Mars
B. Jupiter
C. Mercury
D. Neptune

The value of acceleration due to gravity is minimum on the planet Mercury and maximum on planet Jupiter.

## An orbital velocity of a satellite does not depend on:

B. Mass of the planet
D. Mass of the satellite

Correct Answer: D. Mass of the satellite

An orbital velocity of a satellite does not depend on the mass of the satellite. It depends on the mass and radius of the planet around which it is orbiting. Also, it depends on the radius of the orbit or the height of the satellite.

## What is the dimensional formula of work done?

A. M1 L1 T-1
B. M1 L2 T-1
C. M1 L-1 T-2
D. M1 L2 T-2

Correct Answer: D. M1 L2 T-2

The dimensional formula of work done is M1 L2 T-2. Work is said to be done by a force when the body is displaced actually through some distance in the direction of applied force. The S.I unit of Work is the joule.

## Work done is defined as the dot product of:

A. Force and acceleration
B. Force and area
C. Force and instantaneous velocity
D. Force and displacement

Correct Answer: D. Force and displacement

Work done is defined as the dot product of Force vector and displacement vector. W = F.s Work done is a scalar quantity. Note: Instantaneous power is defined as the dot product of the Force vector and instantaneous velocity.

## The thrust on the rocket is:

A. in the same direction as the rocket
B. in the opposite direction of the rocket
C. at 90° to the direction of the rocket
D. None of the above

Correct Answer: B. in the opposite direction of the rocket

The thrust on the rocket is in the opposite direction of the rocket. The thrust is the force with which the rocket moves upwards. F = -u (dm/dt).

## What is the dot product of two perpendicular vectors?

A. 1
B. 0
C. -1
D. 1/2

When two vectors are perpendicular to each other, then θ = 90° and Cos 90° = 0 . Therefore, A.B = A x B x Cos θ = A x B x Cos 90° = 0.

## What is the apparent weight of the person when the elevator is accelerating downwards?

A. equal to the actual weight
B. greater than the actual weight
C. less than the actual weight
D. Zero