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| 1. |
You slowly lift a book of mass 2 kg at constant velocity a distance of 3m. How much work did you do on the book? |
| Answer» Solution :In this CASE, the force you exert must BALANCE the WEIGHT of the BOOK (otherwise the velocity of the book wouldn't be constant), so F=mg=(2kg)`(10m//s^(2))=20N`. Since this force is straight upward and the displacement of the book is also straight upward, F and d are parallel, so the work DONE by your lifting force is `W=Fd=(20N)(3m)=60N*m`. the work done is 60 J. | |