Question

A car moving along a straight road with speed of144km/h is brought to a stop within a distance of 200m. How long does it take for the car to stop
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Answer 1

QUESTION:

A car moving along a straight road with speed of 144 km/h is brought to a stop within a distance of 200m. How long does it take for the car to stop.

ANSWER:

time taken by car to stop =

2.78 seconds

Explanation:

given that,

A car moving along a straight road with speed of 144km/h

so,

here,

initial velocity of the car = 144 m/s

also given that,

the car is brought to a stop within a distance of 200m.

so,

Here,

final velocity of the car = 0 m/s

[car stops]

distance travelled after applying brakes or stopping it = 200 m

now,

we have,

initial velocity(u) = 144 m/s

final velocity(v) = 0 m/s

distance travelled(s) = 200 m

let the time taken to stop the car be t

by the equation of motion

v² = u² + 2as

where,

a = retardation

putting the values,

(0)² = (144)² + 2a(200)

400a + 20736 = 0

400a = -20736

a = -20736/400

a = -51.84 m/s²

now,

by the equation of motion

v = u + at

putting the values,

0 = 144 + (-51.84)t

-51.84t + 144 = 0

-51.84t = -144

t = -144/-51.84

t = 2.777

t = 2.78 s

so,

time taken by car to stop =

2.78 seconds