Mechanics

11.The SI unit of Young’s modulus of elasticity is
 
A. Dyne/cm
 
B. Newton/m
 
C. Newton/m²
 
D. M CM
 
Option”C” is correct.
The Young’s modulus (E) is a property of the material that tells us how easily it can stretch and deform and is defined as the ratio of tensile stress (σ) to tensile strain (ε). Where stress is the amount of force applied per unit area (σ = F/A) and strain is extension per unit length (ε = dl/l).
12.Which of the following pairs of physical quantities do not have the same dimensional formula?
 
A. Force and pressure
 
B. Work and energy
 
C. Impulse and impulse
 
D. Load and force
 
Option”A” is correct
13.An astronomical unit is related to –
 
A. From the distance between the sun and the earth
 
B. From the distance between the moon and the earth
 
C. The distance between the sun and the moon
 
D. None of the above
 
Option”A” is correct.
It is a unit of length approximating the Sun-Earth distance (of about 150 million kilometres) which is of convenient use in astronomy.
14.Which of the following is a non-dimensional quantity?
 
A. Co-efficient of viscosity
 
B. Strain
 
C. Gas constant
 
D. Plank’s constant
 
Option”A” is correct.

Strain is unitless and dimensionless physical quantity.

Physical Quantity

SI Unit

Dimension Formula

Co-efficient of viscosity

Poiseuille (Kg/m.s or Pa.s)

ML-1T-1

Plank’s constant

Joule-seconds

ML2T-1

Gas constant

Joule/mol.K

ML2T-2K-1

Strain

Unitless

Dimensionless

15.Which of the following is not a vector quantity
 
A. Impulse
 
B. The Speed
 
C. Angular velocity
 
D. Mass
 
Option”D” is correct
16.___________ is a scalar
 
A. Energy
 
B. Torque
 
C. Context
 
D. All of the above
 
Option “A” is correct.
Energy = Work= F*s, here both the force and the time is vector quantity. And we know that the product of two vector quantities give the scalar quantity. So we can say that energy is a scalar quantity.
17.Which of the following is a vector quantity
 
A. Weight
 
B. Pressure
 
C. Energy
 
D. Work
 
Option”A” is correct.
Weight is measurement of the gravitational force applied on the body. As we know that a force has magnitude as well as direction and we call such a quantity as a vector quantity, hence we can say that weight is a vector quantity.
18.Which of the following is not a vector quantity
 
A. Displacement
 
B. Acceleration
 
C. Force
 
D. Distance
 
Option”D” is correct.
Distance is the quantity which is not vector.
19.Which of the following is a vector quantity?
 
A. Velocity
 
B. Mass
 
C. Time
 
D. Length
 
Option”A” is correct.
Velocity has both magnitude as well as direction, so velocity is a vector quantity. 
20.Which of the following is not a derived definition
 
A. Density
 
B. Mass
 
C. Volume
 
D. Acceleration
 
Option”B” is correct

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