Question

A car travelling at 36km/h speeds upto 72km/h in 5 sec. What is ita acceleration? If the same case stops in 20 sec,what is the retardation?​

Answer 1

Answer:

please refer to the attachment

Answer 2

Answer:

u = 36 km/hr = 36 * (5/18) = 10 m/s

v = 72 km/hr = 20 m/s

Using Newton's first eqn. of motion :

v = u + at

20 = 10 + a(5)

Hence a = 2 m/s²

Now the car stops in 20 seconds :

Using the same equation :

v = 0

u = 20 m/s

t = 20 sec

a = ?

0 = 20 + a (20)

a = -1 m/s²

In 2nd case there is retardation of 1 m/s²