Question

the velocity of a car decreases from 40 m per second to 20 metre per second in 4 seconds the retardation of the car is​

Answer 1

initial velocity,u=40m

final velocity,v=20m

acceleration, a=?

time,t=4s

to find retardation we will use the 1st equation of motion

v=u+at

20=40+a×4

20=40+4a

20-40=4a

-20=4a

-20/4=a

-5=a

the retardation is -5

Answer 2

Explanation:

given,

t= 4 sec

v= 20 m/sec

u = 40 m/sec

Now,

v=u + at

=> 20 = 40 + a. 4

=> 20 - 40 = 4a

=> -20 = 4a

=> a = -5 m/sec^2

Hence, the retardation is 5 m/sec^2