## Precalculus (6th Edition) Blitzer

Published by Pearson

# Chapter 6 - Section 6.7 - The Dot Product - Exercise Set - Page 793: 60

#### Answer

The work done is 113 meter-newtons.

#### Work Step by Step

Here, the object moves along the straight line, such that the angle between the force and direction of motion is ${{0}^{\circ }}$. The object is moved from point $\left( 8,11 \right)$ to $\left( 18,20 \right)$. Therefore, the point to which the object has traveled is: \begin{align} & \mathbf{AB}=\left[ \left( 18,20 \right)-\left( 8,11 \right) \right] \\ & =\left[ \left( 18-8 \right),\left( 20-11 \right) \right] \\ & =\left( 10,9 \right) \end{align} $\mathbf{AB}=10\mathbf{i}+9\mathbf{j}$ …… (2) Now, as it is known that: $\mathbf{W}=\mathbf{F}\cdot \mathbf{AB}$ …… (3) Substitute equation (1) and (2) in equation (3), \begin{align} & \mathbf{W}=\left( 5\mathbf{i}+7\mathbf{j} \right)\left( 10\mathbf{i}+9\mathbf{j} \right) \\ & =\left[ \left( 5\times 10 \right)+\left( 7\times 9 \right) \right] \\ & =50+63 \\ & =113 \end{align}

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.