A cyclist is travelling at $15\ ms^{-1}$. She applies brakes so that she does not collide with a wall $18\ m$ away. What deceleration must she have?

Here initial velocity $u=15\ ms^{-1}$

Final velocity $v=0$

Displacement $s=18\ m$

Let $a$ be the deceleration.

On using the equation of the motion: $v^2=u^2+2as$

$0=15^2+2a\times18$

Or $0=225+36a$

Or $36a=-225$

Or $a=-\frac{225}{36}$

Or $a=-6.5\ m/s^2$

Therefore, the deceleration of the car is $6.5\ ms^{-2}$.

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Updated on: 10-Oct-2022

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