A mass m is placed on a rough incline at an angle $\theta$ to the horizon.A force F is applied up the incline,to prevent the mass from sliding down the incline,and it is just enough to prevent the mass from sliding down the incline.Using the compass rose,the direction of the frictional force is along
A)(a)
B)(b)
C)(c)
D)(d)
E)(e)

Question

A mass m is placed on a rough incline at an angle $\theta$ to the horizon.A force F is applied up the incline,to prevent the mass from sliding down the incline,and it is just enough to prevent the mass from sliding down the incline.Using the compass rose,the direction of the frictional force is along 
A)(a) 
B)(b) 
C)(c) 
D)(d) 
E)(e)

Quizplus · Accepted Answer

The direction of the frictional force is always opposite to the direction of motion or impending motion. Since the applied force F is up the incline, the direction of motion or impending motion is down the incline. Therefore, the frictional force must act in the direction opposite to the applied force, which is down the incline. Choice B) shows the frictional force acting in this direction.

A Mass M Is Placed on a Rough Incline at an Angle