Question

a vehicle of mass 120kg is moving with velocity of 90kmph .what force should be applied on the vehicle to stop it in 5s.

Answer 1

90 kmph = 90 * 5/18 m/s = 25 m/s

v = u + at
0 = 25 + 5a
a = -5 m/s^2

F = ma
= -120 * 5
= -600 N

Magnitude of Force to be applied is 600 N

Answer 2

Given: m=120 kg
            u=  90 kmph= 90×5/18= 5×5= 25 m/s
             t= 5 s
Asked: F=?
Solution: We know; a= v-u/t
                                  = 0-25/5
                                  = -25/5
                                  = -5 m/s²
                                F= ma
                                  = 120×(-5)
                                  = -600 kg m/s²
                                  = -600 N