a) At t = 0, mass M = 406 g is sliding on a rough surface at speed v o = 8.53 m/

Question

a) At t = 0, mass M = 406 g is sliding on a rough surface at speed vo = 8.53 m/s. If the friction between the table and M brings it to rest: find W, the word done by friction to bring the mass to rest.
1 J

b) A box of mass M = 462 g is pulled up a frictionless incline that makes an angle ? = 52.8o with the horizontal by a rope parallel to the incline. (For a diagram of this situation: see figure 6-38 on the bottom of page 200 of your textbook.) If the box moves at constant speed v = 5.66 m/s for a distance s = 21.2 m, find:
- W, the work done by the rope: 2 J
- P, the rate at which work is done: 3 W

Explanation / Answer

a)work done by friction=0.5x0.406x8.53^2=14.77J b)work done by rope=0.462x9.8x21.2xsin52.8=--76.46J t=21.2/5.66=3.745sec p=76.46/3.745=20.42W

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