Q21. A bus moving along a straight highway with speed of $72 \mathrm {~km} / \mathrm { h }$ is brought to halt within $4 s$ after applying the brakes. The distance travelled by the bus during this time (Assume the retardation is uniform) is $\_\_\_\_$ m.

Q21. A body moves on a frictionless plane starting from rest. If $S _ { n }$ is distance moved between $t = n - 1$ and $\mathrm { t } = \mathrm { n }$ and $\mathrm { S } _ { \mathrm { n } - 1 }$ is distance moved between $\mathrm { t } = \mathrm { n } - 2$ and $\mathrm { t } = \mathrm { n } - 1$, then the ratio $\frac { \mathrm { S } _ { \mathrm { n } - 1 } } { \mathrm {~S} _ { \mathrm { n } } }$ is $\left( 1 - \frac { 2 } { x } \right)$ for $\mathrm { n } = 10$. The value of $x$ is $\_\_\_\_$ .

A body is projected up the smooth incline plane having angle of inclination $\theta$ with the horizontal as shown in the figure. Find the $v > 0$ distance covered before stopping. (A) $\frac { \mathrm { u } ^ { 2 } } { 2 \mathrm { gsin } \theta }$ (B) $\frac { u ^ { 2 } } { 2 g \tan \theta }$ (C) $\frac { \mathrm { u } ^ { 2 } } { 2 \mathrm {~g} }$ (D) $\frac { u ^ { 2 } } { 2 g \cos \theta }$