Question

This force can either push the block upward at a constant velocity or allow it to slide downward at a constant velocity. The magnitude of the force is different in the two cases, while the directional angle θ is the same. Kinetic friction exists between the block and the wall, and the coefficient of kinetic friction is 0.310. The weight of the block is 47.0 N, and the directional angle for the force F → is θ = 31.0°. Determine the magnitude of F → when the block slides (a) up the wall and (b) down the wall.

Answer 1

(a) Since the force is pushing the block up the wall with a constant velocity, therfore net force on the block in the direction of motion is zero

Forces acting on the block along the wall are-

1. Kinetic Friction, (vertically downward)

(Horizontal component of Force F)

2. Weight ,

3. Vertical component of Force , i.e.

Now, balancing the forces-

(b) In this case friction force will act vertically upward, since the block is sliding down the wall with a constant velocity