# Conceptual Friction problem

## Homework Statement

There is a box drawn on a horizontal surace. A force is being applied at an unkown angle in the positive x direction to the box. The angle is greater than 0 and less than 90. I'm assuming a standard coordinate system.

"In the diagram above the box is stationary as the angle $$\theta$$ is increased. Do the following increase, decrease or stay the same when $$\theta$$ is increased? Explain each answer."

1. Fx
2. Normal Force
3. fs
4. fs-max

None given.

## The Attempt at a Solution

Fx decreases when theta is increased. If the force is broken down into vectors, the geometry of a right triangle tells us that as theta is increased the x-component decreases.

Normal force decreases when theta is increased. Normal force is perpendicular to the surface of contact. When theta increases, the y-component of that force increases. This opposes the force of gravity on the box. The normal force decreases because there is less net force in the negative y-direction.

Static friction decreases because it is dependent on the force applied in the y-direction(in this case). Less normal force equals less static friction here.

The max static friction also decreases because it is dependent on the force applied in the y-direction (in this case). Less normal force equals less max static friction.

Does that seem right to you guys? I feel confident in my answers, but I want to make sure I am not assuming or looking over something. Feedback is always appreciated. Thanks a bunch.

-Mark

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