Question

A particle is acted upon by constant forces $4 \mathbf { i } + \mathbf { j } - 3 \mathbf { k }$ and $3 \mathbf { i } + \mathbf { j } - \mathbf { k }$ which displace it from a point $\mathbf { i } + 2 \mathbf { j } + 3 \mathbf { k }$ to the point $5 \mathbf { i } + 4 \mathbf { j } + \mathbf { k }$. The work done in standard units by the force is given by

• A. 15
• B. 30
• C. 25
• D. 40

Answer 1

Answer: (D)

40

Answer 2

Total force $\vec { F }$ = $( 4 \mathbf { i } + \mathbf { j } - 3 \mathbf { k } ) + ( 3 \mathbf { i } + \mathbf { j } - \mathbf { k } )$ = $7 \mathbf { i } + 2 \mathbf { j } - 4 \mathbf { k }$

Displacement = $( 5 \mathbf { i } + 4 \mathbf { j } + \mathbf { k } ) - ( \mathbf { i } + 2 \mathbf { j } + 3 \mathbf { k } )$ =

Work done = =

= $28 + 4 + 8 = 40$