Question

A cyclist is travelling at 20m/s .She apply break so that does not collide with a wall 18m away. What retardation must she have


RIGHT ANSWER​

Answer 1

Answer :-

She must have a retardation of 11.11 m/s² to avoid collision with the wall .

Explanation :-

We have :-

→ Initial velocity of cyclist (u) = 20 m/s

→ Distance of the wall (s) = 18 m

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To aviod collision with the wall, the cyclist will apply brakes and finally, the cycle will come to rest. So, final velocity (v) of the cyclist will be 0 m/s .

Now, we can calculate retardation (-ve acceleration) of the cyclist by putting values in the 3rd equation of motion .

v² - u² = 2as

⇒ 0 - (20)² = 2a(18)

⇒ -400 = 36a

⇒ a = -400/36

⇒ a = -11.11 m/s²

[Here, -ve sign represents retardation] .