Question

the stopping distance of a car is 40 m when moving with a speed of 80km/h if the car is now moving with 40km/h ,then its stopping distance will be

Answer 1

The stopping distance of the car is 10 m

Explanation:

Let the acceleration of the car is a

Initial speed u =80 km/h

Final speed v = 0

Stopping distance s = 40 m = 0.04 km

Therefore, by using the third equation of motion

$v^2=u^2-2as$

$0^2=80^2-2\times a\times 0.04$

$\implies a=\frac{80\times 80}{2\times 0.04}$

$\implies a=8\times 10^4$ km/h²

Now if the initial velocity u' = 40 km/h

Then, again from the third equation of motion

Stopping distance s'

$s'=\frac{u'^2}{2a}$

$\implies s'=\frac{40\times 40}{2\times 8\times 10^4}$

$\implies s'=10^{-2}$ km

or, $s'=10$ m

Therefore, the stopping distance will be 10 m

Hope this answer is helpful.

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