A particle is displaced from a position ` ( 2 hati - hatj +hatk ) ` to another positions ` (3hati +2hatj -2hatk )` under the action of the force of ` ( 2hati +hatj -hatk )` The work done by the force in an arbitray unit is :

Options

A. 8
B. 10
C. 12
D. 16

Answer

A

Explanation

Work done
` " " W= vec F. vec r `
` = ( 2 hati +hatj - hatk ) .[( 3hati + 2hatj - 2hatk ) - (2hati - hatj +hatk )]`
`= (2hati +hatj - hatk ) . ( hati +3 hatj - 3hatk ) `
`= 2 + 3+ 3`
= 8 unit