Question

A moving train is brought to rest within 20 seconds by applying brakes. find the initial velocity, if the retardation due to brakes is 2 m s–²
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Answer 1

Understanding the question: This question says that we have to find out the initial velocity if a moving train is brought to rest within 20 seconds by applying brakes. And the retardation due to brakes is ${\sf{2 \: ms^{-2}}}$ Let's do it!

Given that:

• Final velocity = ${\sf{0 \: ms^{-1}}}$
• Acceleration = ${\sf{-2 \: ms^{-2}}}$
• Time taken = 20 seconds

Don't be confused!

• Final velocity came as zero because moving train is brought to rest.

• Acceleration came in negative beacuse the train retards.

To calculate:

• The initial velocity

Solution:

• The initial velocity = 40 m/s

Using concept:

• First law of motion

Using formula:

• v = u + at

Where, v denotes final velocity , u denotes initial velocity , a denotes acceleration and t denotes time.

Full Solution:

→ v = u + at

→ 0 = u + (-2)(20)

→ 0 = u + (-40)

→ 0 = u - 40

→ 0 + 40 = u

→ 40 = u

→ u = 40 m/s

→ Initial velocity = 40 m/s

Answer 2

Answer:

Please mark as brainliest...

Step-by-step explanation:

v = u + at

0 = u + (-2)(20)

0 = u + (-40)

0 = u - 40

0 + 40 = u

40 = u

u = 40 m/s

Initial velocity = 40 m/s