Final answer:
The work done when lifting a 15 lb box 9 feet in 5 seconds is 135 lb-ft.
Step-by-step explanation:
Work is defined as the product of force and displacement. In this case, the force is the weight of the box and the displacement is the distance it is lifted. The weight of the box can be calculated using the formula:
Weight = mass x acceleration due to gravity
Since the weight is given as 15 lb, we can find the mass by dividing the weight by the acceleration due to gravity. Assuming the acceleration due to gravity is 32.2 ft/s^2, the mass is:
Mass = Weight / acceleration due to gravity
Once we have the mass and distance, we can calculate the work using the formula:
Work = force x distance
Plugging in the values, we get:
Work = mass x acceleration due to gravity x distance
Work = (15 lb / 32.2 ft/s^2) x 32.2 ft/s^2 x 9 ft
Simplifying, we find that the work done is 135 lb-ft.