Static Friction on an Inclined Plane: Force = mgsin30

[StephenDoty]

A block of mass m is at rest on an inclined plane that makes an angle of 30º with the
horizontal, as shown in the figure. Which of the following statements about the force of
static friction is true?
A) fs > mg D)fs = mg sin 30º
B) fs > mg cos 30º E) None of these statements is true.
C) fs = mg cos 30º

because the only two forces acting on the block is fs and weight, F=0 since at rest, thus 0=fs - mgsin30 so
fs= mgsin30


So the answer is D right??

 

[Doc Al]

Yes. Very good.

 

[Moetasim]

Yes, the correct answer is D) fs = mg sin 30º. This equation represents the relationship between the force of static friction (fs) and the weight of the block (mg) on an inclined plane at an angle of 30º. This is because the force of static friction is equal and opposite to the component of the weight of the block that is parallel to the inclined plane, which is represented by mgsin30º.