Question 1

Which of the following is not a scalar quantity?

Accepted Answer

Work is the scalar product of force and displacement, energy is a scalar quantity, and power is the rate of doing work, which is also a scalar. Momentum, however, is the product of mass and velocity, making it a vector quantity because velocity is a vector. Therefore, momentum is not a scalar quanti

Question 2

What is the dimensional formula of work?

Accepted Answer

Work is defined as the product of force and displacement. The dimensional formula of force is $MLT^{-2}$ and that of displacement is $L$. Multiplying them gives $MLT^{-2} 	imes L = ML^2T^{-2}$, which represents the dimensional formula of work as well as energy.

Question 3

When a conservative force does positive work on a body, the potential energy of the body:

Accepted Answer

The change in potential energy is related to conservative force by $\Delta U = -Wc$. When the conservative force does positive work ($Wc > 0$), the change in potential energy is negative, meaning the potential energy of the body decreases.

Question 4

Which of the following is a non-conservative force?

Accepted Answer

Gravitational force, electrostatic force, and spring force are conservative forces because work done by them along a closed path is zero and depends only on initial and final positions. Frictional force is a non-conservative force because work done against friction depends on the path and energy is

Question 5

The kinetic energy $K$ of a body of mass $m$ and momentum $p$ is given by:

Accepted Answer

Momentum $p = mv$ and kinetic energy $K = \frac{1}{2}mv^2$. Multiplying and dividing by $m$ gives $K = \frac{m^2v^2}{2m} = \frac{p^2}{2m}$.

Work, Energy and Power — MP Board Class 11 Physics Important Questions & Revision Notes