Question

a car of mass 2500 kg moving with a velocity of 20 m per second is stopped in 10 second by applying brakes so the retarding force is

Answer 1

$\textbf{ Hello Mate! }$

Given : Mass of car = 2500 kg

Initial Velocity ( u ) = 20 m/s

Final Velocity ( v ) = 0

Time taken = 10 s

$v = u + at \\ \frac{v - u}{t} = a \\ \frac{0 - 20}{10} = a \\ - 2 \: m {s}^{ - 2} = a$

F = ma

F = 2500 kg × ( -2 m/s^2 )

F = - 5000 N

$\boxed{ \textsf{ \red{ Retardng\:Force\:is\:5000\:N }}}$

Have great future ahead!

Answer 2

Given,

mass  of car (m) = 2500 kg,

initial velocity (u) = 20 m/s

Time (t) = 10 sec

Final velocity (u) = 0  ( As  body  came  to  rest after applying  breaks)

Using  first  equation of  motion,

v = u + at

0 = 20 + 10a

10a = -20

a = -20/10

a = 2 m/s²

Here  negative  sings  shows  that  velocity of  car is decreasing  with a  constant rate.

If  the  retarding  force is F,

F = m × a

F = -2500 × 2

F = -5000 Newton