Question

An automobile starting from the rest speeds up to 15 m/sec. with a constant acceleration of 1.2 m/sec^2 , runs at fast speed for sometime and finally comes to the rest with the deceleration of 1.5 m/sec ^2 . If the total distance travelled is 400 m find the total time required. *

Answer 1

Solution

For first case

Required time

$t_1=\frac{v}{a}\\=\frac{15}{1.2}\\=12.5sec$

Now for second case

$t_2=\frac{v}{a}\\=\frac{15}{1.5}\\=10sec$

So total time required

$t=t_1+t_2\\=12.5+10=22.5sec$