Posted by Subhotosh Khan on August 19, 2002 at 09:19:15:
In Reply to: Vectors posted by Nicholas Edwards on August 16, 2002 at 13:25:32:
: A 32000 lb truck is parked on a 15 degree slope. Assume the only force to overcome is that due to gravity. Find (a) the force required to keeep the truck from rolling down the hill, and (b) the force perpendicular to the hill. How do I do this?
: Answer: (a) 8282.2 lb
: (b) 30,909.6 lb
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This problem needs picture (called free-body diagram)
You have three forces acting on the truck:
1) gravitational force - vertically down(W = 32000)
2) friction force (Q) - pointed up the slope parallel to plane
3) Normal force (N) - pointed up perpendicular to the plane
Now make your 'x' and 'y' axis along and perpendicular to the plane. Apply law of equilibrium of forces (Newton's First Law)
Fx = 0 = Q - W*sin 15
Fy = 0 = N - W*cos 15
Now you have two equations and two unknowns ('Q' and 'N') - solve it....