Question

A body of mass 10 kg moves in positive x-direction at a constant speed of 10 m/s. A constant force then acts for 4 sec on the body and gives it a speed of 2m/s in opposite direction. The force acting on the body is

Answer 1

force acting on the body is equal to
(mass)(acceleration)
acceleration = (change in velocity)/(time taken)
as velocity is vector quantity
initial velocity is 10m/s
then final velocity will be -2m/s..
here minus sign indicates opposite direction
so acceleration = [10 - (-2)]/4
so acceleration = 3 m/(s^2)
now force = (mass)(acceleration)
force = (10)(3)
force = 30N