Question

A force 2i+j-k Newton acts on a body which is initially at rest.if the velocity of the body at the end of 20 seconds is 4î+2j+2k meter seconds, the mass of the body is

Answer 1

We know that

F=ma

a can be written as (dv)/dt

So,

F. dt = m. dv

Now integrating both sides we get

F . t = m. v

Initially body started from rest so,

At t=0 , v=0

Now,

Substituting the above values given in the question we get,

(2i + j -k)×20 = (4i + 2j - 2k)× m

m = (20 × (2i + j -k)) / (4i + 2j - 2k)

Taking mod, we get

m=10 kg

So,

The mass of the body was 10kg

Answer 2

Answer is in the Above Picture..