A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed

English

Gujarati

Hindi

4-1.Newton's Laws of Motion

medium

A constant retarding force of $50\; N$ is applied to a body of mass $20\; kg$ moving initially with a speed of $15\; m/s$. How long (in $sec$) does the body take to stop ?

$6$

$5$

$3$

$8$

Retarding force, $F=-50 \,N$

Mass of the body, $m=20 \,kg$

Initial velocity of the body, $u=15 \,m / s$

Final velocity of the body, $v=0$

Using Newton's second law of motion, the acceleration ( $a$ ) produced in the body can be calculated as:

$F=m a$

$-50=20 \times a$

$\therefore a=\frac{-50}{20}=-2.5 \,m / s ^{2}$

Using the first equation of motion, the time ( $t$ ) taken by the body to come to rest can

be calculated as: $v=u+a t$

$\therefore t=\frac{-u}{a}=\frac{-15}{-2.5}=6\;s$

Standard 11

Physics

medium

medium

hard

medium

easy