Question

A car is being driven at a speed of 20 ms-1 when brakes are applied to bring it to rest in 5s. The deceleration produced in this case will be a) +4 ms-2 b) ‒4 ms-2 c) ‒0.25 ms-2 d) +0.25 ms-2

Answer 1

Given,
Initial velocity , u = 20 m/s
time taken to stop the car , t = 5sec
A/C to question, after 5 sec car brings to rest.
so, final velocity of car , v = 0 m/s

Use formula,
v = u + at,
0 = 20 + a5
5a = -20 ⇒ a = -4 m/s²
Here negative sign indicates that motion is retarding .

Hence, option (b) is correct

Answer 2

HEY DEAR ... ✌️

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=) Given,
Initial velocity (u) = 20 m/s

Time taken (t) = 5 sec

We know , after 5 sec car brings to rest .
So , final velocity of car will be v = 0 m/s

Also , we know .

=) v = u + at

putting the values .

=) 0 = 20 + 5a

=) 5a = -20

=) a = -4 m/s^2

Option (b) is the correct answer .

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HOPE , IT HELPS ... ✌️