(a) Define the term 'energy' of a body. What is the SI unit of energy.(b) What are the various forms of energy?(c) Two bodies having equal masses are moving with uniform speeds of v and 2v respectively. Find the ratio of their kinetic energies.

Academic Physics NCERT Class 9

(a) Energy- The ability of a body to do work is known as the energy of a body. The SI unit of energy is $Joule$.

(b) Below are the various form of energy:

Potential energy, kinetic energy, sound energy, light energy, chemical energy, and electrical energy are the various form of energy.

(c) Let $m$ be the mass of two bodies.

Therefore, the kinetic energy of the body with $v$ velocity $K_1=\frac{1}{2}mv^2$

Kinetic energy of the body with $2v$ velocity $K_2=\frac{1}{2}m(2v)^2$

Or $K_2=4\times\frac{1}{2}mv^2$

Ratio of the kinetic energies $\frac{K_1}{K_2}=\frac{\frac{1}{2}mv^2}{4\times\frac{1}{2}mv^2}$

Or $\frac{K_1}{K_2}=\frac{1}{4}$

Or $K_1:K_2=1:4$

Simply Easy Learning

Updated on: 10-Oct-2022

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