Question

a car is moving with a uniform velocity 72 Km/hr . on applying breaks it comes to rest after traveling a distance of 200m. calculate the retardation and tike taken to come to rest.
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Answer 1

Answer:

retardation = 1m/s

time taken to come to rest = 20 seconds

Explanation:

u=72km/hr = 20m/s

v = 0

s = 200m

v² - u² = 2as

0 - 20² = 2*a*200

-400 = 400a

a = -1m/s²

ie. retardation = 1m/s²

v = u+at

0 = 20 + -1 * t

0 = 20 - t

t = 20 sec

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Answer 2

Given :-

• A car is moving with a uniform velocity 72 Km/hr . on applying breaks it comes to rest after traveling a distance of 200m.

To find :-

• Retardation
• Time taken to come in rest

Solution :-

• Initial velocity (u) = 72km/h

• Distance travelled (s) = 200m

• Final velocity (v) = 0

→ Initial velocity = 72km/h

→ u = 72 × 5/18

→ u = 20m/s

According to third equation of motion

→ v² = u² + 2as

→ (0)² = (20)² + 2 × a × 200

→ 0 = 400 + 400a

→ - 400 = 400a

→ a = -400/400

→ a = - 1m/s²

Therefore

• Retardation of car is 1m/s²

According to first equation of motion

→ v = u + at

→ 0 = 20 + (-1) × t

→ 0 = 20 - t

→ t = 20s

Hence,

• Time taken to come in rest is 20s