- #1
physicsgirl199
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Homework Statement
An 80 kg object is on top of a 40°ramp and held by a box that is filled with sand bags. Each sand bag has a mass of 12 kg, the static friction coefficient between the box and the ramp is .507. What is the least amount of sand bags needed to prevent the object from sliding.
Homework Equations
F,net,,x,object = 0 = F(box) - F(grav,x)
F(box) = F(grav,x,obj)
F,net,box = friction - F(object) - F(grav,x,box)
friction = μ(s)mgcos(40°)
F(grav,x,box) = mgsin(40°)
F(object) = mg(sin°40)
The Attempt at a Solution
F(box) = F,grav,x,obj = 504 N
F,net,box = friction - F(obj) - F,grav,x,box
= > μ(s)mg(cos40) - 504 - mg(sin40) = 504
=> m[μ(s)gcos40 - gsin40] = 1008
=> m = 1008/(-2.49) = -404 kg ??
so lost