Question

A moving train is brought to rest between 20 seconds by applying brakes find the initial velocity if the retardation due to brakes is 2 m/s^2.

Answer 1

Given : -

•Final velocity of train is = 0

•Acceleration of train is = -2m/s^2.

•Time taken by applying brakes in train = 20 seconds.

To Find : -

•Initial velocity of train = ?

Solution : -

Given,

• v = 0
• a = -2m/s^2
• t = 20sec

we have,

$\: \sf \large \implies \: v = u + at$

Now put the values here

$\: \sf \implies 0 = u - 2 \frac{m}{ {s}^{2} } \times 20s \\ \\ \: \sf \implies \: u = 40 \frac{m}{s}$

Thus,the initial velocity of the train is 40m/s.

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Answer 2

Answer:

Explanation:

Given,

• Final velocity of the train, v = 0 m/s (As it brought to rest)
• Time taken by the train, t = 20 seconds
• Retardation by train, a = - 2 m/s².

To Find,

• Initial velocity of the train, u = ?

Formula to be used,

• According to 1st equation of motion, we know that
• v = u + at

Solution,

Putting all the values, we get

v = u + at

⇒ 0 = u + (- 2) × 20

⇒ - u = - 40

⇒ u = 40 m/s

Hence, the initial velocity of the train is 40 m/s.