Question

instead of lifting the 300 pounds of hay into the 15 - foot loft by herself, fran decides to use a horse that can pull with 100 watts of power (similar to figure 4). how long will it take her now? (3 points)

Explanation:

Step1: Calculate work done

First, convert weight to force (in pounds-force, which is equivalent here), then calculate work as force × distance.
$W = 300\ \text{lb} \times 15\ \text{ft} = 4500\ \text{ft-lb}$

Step2: Convert power to ft-lb/s

Use the conversion $1\ \text{Watt} = 0.737562\ \text{ft-lb/s}$.
$P = 100\ \text{W} \times 0.737562\ \frac{\text{ft-lb/s}}{\text{W}} = 73.7562\ \text{ft-lb/s}$

Step3: Solve for time

Use $t = \frac{W}{P}$ to find time.
$t = \frac{4500\ \text{ft-lb}}{73.7562\ \text{ft-lb/s}} \approx 61.01\ \text{seconds}$

Answer:

Approximately 61 seconds (or 61.01 seconds for more precision)