Answered

A student lifts a 90 pound (lb) ball 4 feet (ft) in 5 seconds (s). How many joules of work has the student completed?

A770J
B369J
C488 ft lbs
D488.6 J

Verified Answer :

AL2006


Wending your way through this question and the list of choices
is like running through a corn-maze on a moonless night with
your eyes closed.

Work = (force) x (distance)

Keeping with the units used In the question ...

       Work = (90 pounds) x (4 feet)  =  360 foot-pounds .

If you want the work expressed in joules, then you need to convert
pounds and feet to newtons and meters.

           (90 pounds) x (4.448 newtons/pound) =  400.32 Newtons

               (4 feet) x (1 meter / 3.28084 feet)  =  1.219 meters

Work = (force) x (distance)

          = (400.32 newtons) x (1.219 meters) = 488.1 joules .

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