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A force (3hati+4hatj) newton acts on a b...

A force `(3hati+4hatj)` newton acts on a boby and displaces it by `(3hati+4hatj)` metre. The work done by the force is

A

`25`

B

`40`

C

`16`

D

`8`

Text Solution

Verified by Experts

The correct Answer is:
A
Displacement `dvec(r)=dxhat(i)+dyhat(j)`
but `3y+kx=5` so `3dy+kdx=0`
`rArr dvec(r)=dxhat(i)-k/3 dx hat(j)=(hat(i)-k/3 hat(j))dx`
Work done is zero if `vec(F).dvec(r)=0`
`(2hat(i)+3hat(j)).(hat(i)-k/3 hat(j))dx=0 rArr (2-k)dx=0 rArr k=2`
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