A car accelerates from 0 km/h to 100 km/h in 5 seconds. It can decelerate at 5 m/s, if the driver applies the brakes fully. What is the acceleration of the car?

Expert Answers

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Acceleration is defined as the rate of change of velocity. That is, 

acceleration, a = dv/dt

Here, the velocity of the car increases from 0 km/h to 100 km/h in 5 seconds. Let us first convert the velocity to m/s units, using the knowledge that 1 km is equal to 1000 m and 1 hour has 3600 seconds.

Thus, 0 km/h = 0 m/s

and , 100 km/h = (100 x 1000) m/(1 x 3600) s = 27.8 m/s

Thus, the acceleration of the car is:

a = (27.8 - 0)(m/s) / 5 s = 5.6 m/s^2

Thus the car has an acceleration of 5.6 m/s^2.

If the car can decelerate at 5 m/s^2, then it would need

t = (v - u)/a = (0 - 27.8) / 5 = 5.56 sec to stop completely.

Hope this helps. 


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