A force ` (2hat I + hat j - hat k)N` acts on a body which is initially at rest. At the end of 20 sec the velocity of the body is `(4 hat i + 2 hat j – 2 hat k) ms^(-1)`,then mass of the body is

Options

A. 8 kg
B. 10 kg
C. 5 kg
D. 4.5 kg

Answer

B

Explanation

The magnitude of force, `F=sqrt(4+1+1)=sqrt(6)`
The speed or magnitude of velocity,`v=sqrt(16+4+4)=sqrt(24)`
As, `F=(dp)/(dt)=m((v-u)/(t))`
where, m=mass of body
`Rightarrow sqrt(6)=m((sqrt(24)-0)/(20))Rightarrowm=(sqrt(6)xx20)/(sqrt(24))=(20)/(2)=10Rightarrowm=10g`