Question

a car moving at speed of 72 km per hour and applied brake which provide retardation of 5 metre per second how much time does the car take taken to stop​

Answer 1

Answer:

t=4sec

Explanation:

Given-

u=72km/h

To convert km/h into m/s

=72×5/18

=20m/s

v=0

a=-5m/s^2

t=?

v=u+at

0=20+(-5)×t

-20=-5×t

t=-20/-5

t=4sec

Answer 2

Answer:

Change the given speed in m/s

72 km / h = 72 *1000/3600 (formula for conversion

Therefore speed = 20 m/s

Now acceleration= - 5 m/s² ( - ve because it is retardation)

Using first equation of motion

=> v = u + at

Final speed = 0

So => 0 = 20 + (-5) t

5t = 20

Therefore t = 4 seconds

Explanation:

The answer itself is well explained