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# force needed to drag a sack of rice

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1. What force is required to drag a sack of rice weighing 105 lb if the coefficient of friction is 0.25?
(a) when the force is parallel to the surface,
(b) when the force makes 37° above the horizontal.

2. A piano weighing 600 lb is to be raised to a platform 4 ft high through a plank 10 ft long. If the coefficient of friction is 0.30, what force parallel to the plank will be needed?

https://brainmass.com/physics/newtons-laws/force-needed-drag-sack-rice-196237

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friction
1. what horizontal force is required to drag a sack of rice weighing 105 lb if the coefficient of friction is 0.25? (a) when the force is parallel to the surface,

First draw the free body diagram.
The normal force N = weight = 105 lb.
Therefore, the friction f = µN = 0.25 * 105 = 26.25 lb.
Then the dragging force F = f = 26.25 lb.

(b) when the force makes 37° above the horizontal.

Still, the net force on the rice is 0.
In the vertical direction,
N + Fsin37° = W (1)
In the horizontal direction,
f = Fcos37° (2)
and we know that f = µN = 0.25 N (3)
Substituting (3) to (2) gives
N = 4Fcos37° (4)
Substituting (4) to (1) gives
F(4cos37° + sin37°) = W
F = 105 / (4cos37° + sin37°) = 27.67 lb.

2. a piano weighing 600 lb is to be raised to a platform 4 ft high through a plank 10 ft long. if the coefficient of friction is 0.30, what force parallel to the plank will be needed?

The angle of the plank is
In the direction perpendicular to the plank,

So the friction

In the direction parallel to the plank,

force parallel to the plank is 404.97 lb.

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!