Find the work done by a force $\mathbf { F } = \mathbf { i } + 5 \mathbf { j } + 7 \mathbf { k }$ that moves an object from the point $( 3,0,5 )$ to the point $( 7,5,10 )$ along a straight line. The distance is measured in meters and the force in newtons.
Select the correct answer.
A) $64 \mathrm {~J}$
B) $74 \mathrm {~J}$
C) $84 \mathrm {~J}$
D) $94 \mathrm {~J}$
E) $104 \mathrm {~J}$

Question

Quizplus · Accepted Answer

The work done by a force is given by the dot product of the force and the displacement. In this case, the force is $\mathbf { F } = \mathbf { i } + 5 \mathbf { j } + 7 \mathbf { k }$ and the displacement is $\mathbf { d } = \mathbf { 7 } - \mathbf { 3 } = 4 \mathbf { i } + 5 \mathbf { j } + 5 \mathbf { k }$. Therefore, the work done is$$W = \mathbf { F } \cdot \mathbf { d } = (1)(4) + (5)(5) + (7)(5) = 64 \mathrm {~J}$$

Find the Work Done by a Force F=i+5j+7k\mathbf { F } = \mathbf { i } + 5 \mathbf { j } + 7 \mathbf { k }F=i+5j+7k

Find the Work Done by a Force $\mathbf { F } = \mathbf { i } + 5 \mathbf { j } + 7 \mathbf { k }$