Will the block move with a parallel force?

[ron_jay]

Homework Statement

A block of mass 2 kg is pushed against a rough vertical wall with a force of 40N , co-efficient of static friction being 0.5.Another horizontal force of 15N is applied on the block in the direction parallel to the wall.

Homework Equations

Will the block move? If yes, in which direction? If no, find the frictional force exerted by the wall on the block

The Attempt at a Solution

The first thing which puzzles me about this problem is that in which direction should the parallel force be acting? I think the block will move;but do we take into consideration the gravitational force acting downwards?

 

[PhanthomJay]

The problem statement is incomplete as worded. It should state in which direction (up or down) the parallel force is acting. Does it?

 

[Doc Al]

The first thing which puzzles me about this problem is that in which direction should the parallel force be acting?

Sideways! (I admit that that's tricky.)

I think the block will move;but do we take into consideration the gravitational force acting downwards?

You need to consider all forces acting parallel to the wall, including gravity.

 

[ron_jay]

Well the problem doesn't state that but what would be the solution both ways(for up and down)?

 

[PhanthomJay]

Well the problem doesn't state that but what would be the solution both ways(for up and down)?

Oh, sorry, Doc is right, forget my response, as i was envisioning a vertical force parallel to the wall.

 

[ron_jay]

Ok...could you elaborate a little on how the net motion is sideways?

 

[Doc Al]

First identify all the forces acting on the block parallel to the wall. Without friction, what would be the net force parallel to the wall (magnitude and direction)? Is friction enough to prevent the motion?