A car is moving at a constant speed 30 m/sec. at a distance of 100 m there is a obstacle immediately brakes are applied which give constant retardation 6 m/s.what is the distance from the wall after 12 s.?

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Answer 1 · 2014-12-25T16:35:02

We have to bring our speed back to 0.

With a retardation of $6 \frac{m}{s^{2}}$ $6m/s^2$ this will take $\frac{30}{6} = 5$ $30/6=5$ seconds

In these 5 seconds we go from a speed of 30 m/s to 0 m/s.
During these 5 seconds we can say that our average speed was:

$\frac{30 - 0}{2} = 15 \frac{m}{s}$ $(30-0)/2=15 m/s$

Since distance=average speed x time, we come up with:

$d = 15 \cdot 5 = 75$ $d=15*5=75$ m, which is $100 - 75 = 25$ $100-75=25$ m from the wall

Answer:
The car stops 25 meter from the wall after 5 seconds.

Extra
To answer the complete question: If the driver does not decide to move his vehicle, it will still be 25 m from the wall after 12 s.