Kinetic Energy

Objects in motion possess energy and can do work. This energy is called Kinetic Energy.
F = ma.
Also W = F.s
⇒ From the 2nd equation of motion v2−u2=2as,
⇒ we get s = v2−u2 / 2a

Substituting equation for work done by a moving body,
⇒ we get W =m.a *
v2−u2 / 2a

Or

Kinetic Energy = K.E= 1/2 mv2 (taking initial velocity u=0)

When two identical bodies are in motion, the body with a higher velocity has more K.E.

Work-energy theorem

The work-energy theorem states that the net work done by a moving body can be calculated by finding the change in KE.

Wnet = KEfinal− KEinitial

Wnet = 1/2 mv2

Factors affecting kinetic energy

  • Mass
  • Velocity
  • Momentum

Potential Energy

Energy can get stored in an object when work is done on it.

For example, stretching a rubber string. The energy that is possessed by a body by virtue of its configuration or change in position is known as Potential Energy.

The potential energy of an object at a height.
When an object is raised to a certain height, work is done against gravity to change its position. This energy is stored as Potential Energy.

W = F.s

F = ma
In the case of increasing the height, F = mg

Therefore, W (P.E) = mgh
⇒ ΔPE = mg(hfinal - hinitial )

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