Question

A car running at 72 km his slowed down to 18 km h by the
application of brakes over a distance of 20 m. Calculate acceleration of car
If the brakes are applied with the same force calculate total time in which
car stops and total distance covered by it?
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Answer 1

As the brakes are applied with the same force so the acceleration will be constant.

Using the equation of motion,

v²=u²+2as

⇒102 = 202 + 2 * a * 25

⇒50a = 100 − 400

⇒a = −30050 = − 6 m/s²

#The negative sign shows the retardation.

(i) Let us find out the total time in which the car comes to rest. As the car comes to rest so the final velocity, v = 0

v = u + at

⇒0= 20−6t

⇒t= 206= 103 s

(ii) The distance travelled by it,

v²=u²+2as

⇒0=202+2*(−6)*s

⇒12s=400

⇒s=4006

=66.67 m

Answer is 66.57 m....

Hope it helps you dear.......xd

Answer 2

Answer:

999.999 time meter per second

Explanation:

v=72km

u=18km

distance=20meter

1. km convert in meter. because SI unit of acceleration is =meter per second.
2. when convert 72 km in meter answer is 1000 meter
3. when convert 18 km in meter answer is 0.001 meter

then acceleration formula is = change in velocity upon time taken .

v-u upon t.

1. 1000-0.001 upon t

999.999 time meter per second