When a liquid is heated at constant pressure to its boiling point or when the pressure is reduced at a constant temperature it will convert to a gas. This process of a liquid changing to a gas is called evaporation.

(i) When amplitudes of the vibrating pendulum is small then pendulum is small. Here the restoring force F = mg sin θ = mg θ = mgx/l .
(ii) Where x is the displacement of the bob and I is the length of pendulum. Hence F x x. Since F is directed towards mean position.
(ill) Therefore the motion of the bob of simple pendulum will be S.H.M. if θ is small.

This is conductor when we are without clothes air carries away heat from our body clue to convection & hence we feel cold.

i) The evaporation of a liquid from its surface occur so some molecule acquire velocities sufficient enough to escape from the attractive force at the surface.
ii) Because escaping molecule have higher K.E, hence the average K.E of molecules left behind decreases.
iii) As average K.E is directly related with temperature hence evacuation causes cooling.

\(\text {The gravitational field }=-\frac{G m}{r^{2}} \hat{r} \)
\(\frac{G m}{x^{2}}=\frac{G \times 4 m}{(r-x)^{2}} \)
\(\frac{m}{x^{2}}=\frac{4 m}{(r-x)^{2}} \)
\(\frac{1}{x^{2}}=\frac{4}{(r-x)^{2}} \)
\(\frac{1}{x}=\frac{2}{r-x}\)
r - x = 2x
\(\mathrm{r}=3 x \quad \therefore x=\frac{r}{3} \)
\(\text {Gravitational potential } \mathrm{V}=-\frac{G m}{r}=-\frac{9 \mathrm{Gm}}{r}\)

Acceleration of the object, Speed of the object when it reaches the bottom

(i) Torque \(\overrightarrow { t } =\overrightarrow { r } \times \overrightarrow { F } \). where F is Force and \(\overrightarrow { r } \) is position vector of a particle
(ii) Angular momentum \(\overrightarrow { L } =\overrightarrow { r } \times \overrightarrow { p }\ where\ \overrightarrow { p } \)  is the linear momentum 
(iii) Linear Velocity \(\overrightarrow { v } =\overrightarrow { \omega } \times \overrightarrow { r } \)  where \(\overrightarrow { \omega } \) is angular velocity.

(i) For an isolated system, the sum of all forms of energy i.e., the total energy remains the same in any process irrespective of whatever internal changes may take place.
(ii) This means that the energy disappearing in one form reappears in another form. This is known as the law of conservation of energy.

The direction of torque is found using right hand rule. This rule says that if fingers of right hand are kept along the position vector with palm facing the direction of the force and when the fingers are curled the thumb points to the direction of the torque.

(i) Physics is a branch of science.
(ii) The word comes from a Greek word meaning 'nature'.
(iii) It deals with the study of nature and natural phenomena.