A car travelling at $72 k m / h$ decelerates uniformly at $2 m / s^{2}$ . Calculate (a) the distance it goes before it stops, (b) the time it takes to stop, and (c) the distance it travels during the first and third seconds.

Open in App

Solution

$u_{i n i t i a l} = 72 \times \frac{5}{18} = 20 m / s$
$a_{d e c} = 2 m / s^{2}$
(a) $s = u t + \frac{1}{2} a t^{2}$
$v = u + a t$
$v = 0$
$u - a_{d e c} t = 0$
$20 = 2 \times 1$
$t = 10 s$
$s = 20 \times 10 - \frac{1}{2} \times 2 \times 100$
$s = 100 m$
(b) $t = 10 s$
(c) $s_{n t h} = u + \frac{a}{2} (2 n - 1)$
$s_{1 s t} = 20 - \frac{2}{2} (2 \times 1 - 1)$
$s_{1 s t} = 19 m$
$s_{3 r d} = 20 - \frac{2}{2} (2 \times 3 - 1)$
$s_{3 r d} = 15 m$

Suggest Corrections

Similar questions

Q. A particle starts from rest, accelerates at

2 m / s^{2}

for

10 s

and then goes for constant speed for

30 s

and then decelerates at

4 m / s^{2}

till it stops. What is the distance travelled by it?

Q. A car is travelling with a speed of 36km/h. The driver applies brakes retards the car uniformly. The car is stopped in 5seconds. Find the retardation of the car and the distance travelled before it is stopped.

Q. A car weighing 600 kg traveling with

72 k m / h

stops at a distance of

60 m

decelerating uniformly. What is the work done by brakes in joules?

The brakes applied to a car produce a negative acceleration of $a = 6 m s^{- 2}$ . If the car takes 2 seconds to stop after applying the brakes, calculate the distance it travels during this time. (Give your answer in m).

A car weighing $1000$ $k g$ and travelling at $30$ $m / s$ stops at a distance of $50$ $m$ decelerating uniformly. What is the force exerted on it by the brakes?

Join BYJU'S Learning Program

A car travelling at 72 km/h decelerates uniformly at 2m/s2. Calculate (a) the distance it goes before it stops, (b) the time it takes to stop, and (c) the distance it travels during the first and third seconds.

uinitial=72×518=20m/sadec=2m/s2(a)s=ut+12at2v=u+atv=0u−adect=020=2×1t=10ss=20×10−12×2×100s=100m(b)t=10s(c)snth=u+a2(2n−1)s1st=20−22(2×1−1)s1st=19ms3rd=20−22(2×3−1)s3rd=15m

A car travelling at $72 k m / h$ decelerates uniformly at $2 m / s^{2}$ . Calculate (a) the distance it goes before it stops, (b) the time it takes to stop, and (c) the distance it travels during the first and third seconds.