Question

a train is travelling at a speed of 72km/h.Brakes are applied so as to produce a uniform acceleration of -0.5 m/s²
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Answer 1

Answer:

1000 m

Explanation:

Here, we have

Initial velocity, u = 72 km/h = = 72 × 5/18 = 20 m/s

Final velocity, v = 0 (As brakes applied)

Acceleration, a = -0.2 m/s²

To Find,

Distance traveled s = ?

According to the 3rd equation of motion,

We know that,

v² - u² = 2as

So, putting all the values, we get

⇒ v² - u² = 2as

⇒ (0)² - (20)² = 2 × (- 0.2) × s

⇒ 400 = - 0.4s

⇒ 400/- 0.4 = s

⇒ s = 1000 m or 1 km.

Hence, the distance traveled by train is 1000 m or 1 km.

Answer 2

Initial velocity, u = 72 kmph = 20 m/s

Final velocity, v = 36 kmph = 10 m/s

displacement, s = 200 m

let acceleration be a.

using 3rd equation of motion,

a = (v2-u2)/2s = -3/4 m/s2

now final velocity =0 m/s

let final displacement from this position

be s

again using 3rd equation of motion,

s = (v2-u2)/2a = 200/3 m