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Blupig · #1 12-05-2010, 06:45 PM

I've got 2 questions here that are really making me bust a nut:

Quote:

A rope exerts a force of magnitude 21N, at an angle of 31 degrees above the horizontal, on a box at rest on a horizontal floor. The coefficients of friction between the box and the floor are µ(s) = 0.55 and µ(k) = 0.50. The box remains at rest. Determine the smallest possible mass of the box.

Quote:

A skier on a slope inclined at 4.7 degrees to the horizontal pushes on ski poles and starts down the slope. The initial speed is 2.7m/s. The coefficient of kinetic friction between skis and snow is 0.11. Determine how far the skier will slide before coming to rest.

I've got an idea on how to do both, but in both instances my ideas are wrong >_>

confuego116 · #2 12-05-2010, 09:19 PM

For the first one:

m = -{[(cos31)(21N)]/(0.55)} - (sin31)(21N)---- divide that by 9.8 or 10.

Check to see if my sin and cos are right. Everything else should be right.

My equations:

SUM F up and down = Fn + Ry(rope) - Fg=ma
SUM F left and right = Rx - Ff=ma