Kinetic Energy - Practice Questions & MCQ

•  Mechanical Energy-

                 Mechanical energy is the sum of potential energy and kinetic energy. It is the energy associated with the motion and

                 position of an object.

• Kinetic energy

                 The energy possessed by a body by virtue of its motion is called kinetic energy.

                 E.g-Moving vehicle possesses kinetic energy.

1. The expression for kinetic energy             

$
K . E .=\frac{1}{2} m v^2
$

Where $m \rightarrow$ mass
$v \rightarrow$ velocity
2. Kinetic Energy is always positive.
3. Kinetic energy depends on the frame of reference -

The kinetic energy of a person of mass $m$, sitting in a bus moving with speed $v$, is zero in the frame of the bus but it is equal to $\frac{1}{2} m v^2$ in the frame of the earth.
4. Work-energy theorem-

Net work done by all the forces acting on a particle is equal to change in its kinetic energy.

$
\begin{aligned}
W & =\frac{1}{2} m v^2-\frac{1}{2} m v_0^2 \\
W & =k_f-k_i
\end{aligned}
$

$
\begin{aligned}
& \text { Where } m=\text { mass of the body } \\
& \qquad \begin{aligned}
v_0 & =\text { initial velocity } \\
v & =\text { final velocity }
\end{aligned}
\end{aligned}
$
 

This theorem is valid for a system in the presence of all types of forces (external or internal, conservative or no conservative).
5. Relation of kinetic energy with linear momentum

$
k=\frac{m v^2}{2}
$

and $\mathrm{P}=\mathrm{mv}$ or $\mathrm{v}=\mathrm{p} / \mathrm{m}$ $\qquad$
put this value of $v$ in equation (1)
Put we get $k=\frac{p^2}{2 m}$
Where $p \rightarrow$ momentum