A force of 4N acts on a body of mass 2kg for 4s. Assuming the body to be initially at rest, find

a) its velocity when the force stops acting.

b) the distance covered in 10s after the force starts acting.

F = m(dv/dt)

so,

dv = (F/m).dt

here

F = 4N

m = 2kg

dt = 4s

thus, the velocity will be

dv = (4/2).4

so,

dv = 8 m/s

acceleration

a = dv/dt = 8/4 = 2 m/s²

distance covered while force is acting

s₁ = (v² - u²) / 2a

 = (8² - 0) / 2x2

or

s₁ = 16 m

..

(b)

distance covered while force is not acting

s₂ = ut + (1/2)at²

here,

u = 8 m/s

t = 10s - 4s = 6s

a = 0

so,

s₂ = 8x6 = 48m

thus,

the total distance travelled

S = s₁ + s₂ = 16m + 48m

or

S = 64m