Question

a car travels with a a velocity of 72 km/h and change it's its velocity to 36km/h in 2 hrs Calculate the retardation of the car.​

Answer 1

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

Explanation:

Answer 2

Answer:

v=u+at

36=72+A2

36-72=A2

A2=-36

-36÷2=a

a = -18 km per hour