Question

please do the numerical ​

Answer 1

Initial velocity, u = 20 m/s

Final velocity, v = 0 m/s

Time , t = 5 s

We know that

v = u + at

Putting values

0 = 20 + 5a

5a = - 20

a = -4

Hence the acceleration is -4 m/s^2 .

Here minus sign indicates that the direction of acceleration is opposite to its velocity.

Answer 2

The retardation is 4 m s⁻²

Explanation:

• Retardation is the negative acceleration that is final velocity reduces as compare to initial velocity with time
• Retardation have same unit and dimension as that of acceleration and is a vector quantity

$acceleration = \frac{change in velocity}{time taken}$

=> change in velocity = final velocity - initial velocity

given, initial velocity = 20 m s⁻¹

final velocity = 0 m s⁻¹

time taken = 5 s

=> $acceleration = \frac{0-20}{5}$

=> acceleration = -4 m s⁻²

=> retardation = 4 m s⁻²

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