A car of mass 1500kg is travelling at 10 ms-1 along a horizontal road. A brake force of 3000N brings it to rest. Calculate the deceleration of the car and the distance travelled by the car whilst decelerating.
To calculate the deceleration of the car we must re-arrange F=ma to make a the subject of the formula, a = F/m. We then put in the numbers to get, 3000/1500, to get a deceleration of 2 ms^-2.
To get the distance the car has travelled we need to use one of our SUVAT equations. We know initial velocity, u = 10, the final velocity, v = 0 as the car is at rest, the acceleration, a = -2, and we want to find the distance, s. We therefore select the equation with these terms in which is v^2 = u^2 + 2as. We re-arrange to make s the subject of the formula, (v^2 - u^2)/2a = s, and sub in the numbers, to get -(10^2)/2*-2 = 25m.
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