Forces acting on a block that is pushed against a wall

Thread starter MatinSAR
Start date Feb 28, 2023
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Block Forces Wall

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Feb 28, 2023

MatinSAR

Homework Statement: What should be the magnitude of force F so that the object is definitely moving?(Frictional force is equal to 0.5 for each newton of vertical force on the surface.)
A)25 B)30 C)40 D)50

Relevant Equations: ##F_{net} =ma##
##f_{s} =µ_sN##
##f_{k} =µ_kN##

Picture of problem:

For the object to be moving, it must overcome friction.

##f=0.5*0.6F = 0.3F##
##mg=22N##

Upward motion:
##0.8F>mg+f \rightarrow 0.5F>22 \rightarrow F>44N ##

Downward motion:
##0.8F+f<mg \rightarrow 1.1F<22 \rightarrow F<20N ##

I think correct option is D. Can you please guide me if I'm wrong?

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Feb 28, 2023

TSny

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Your work looks good to me.

Feb 28, 2023

MatinSAR

TSny said:

Your work looks good to me.

Thank you for your help.

FAQ: Forces acting on a block that is pushed against a wall

What are the main forces acting on a block that is pushed against a wall?

The main forces acting on a block that is pushed against a wall are the applied force, the normal force from the wall, the gravitational force, and the frictional force. The applied force is the force exerted to push the block against the wall. The normal force is the perpendicular force exerted by the wall on the block. The gravitational force acts downward due to the weight of the block. The frictional force acts parallel to the wall and opposes the motion or potential motion of the block.

How does the normal force from the wall affect the block?

The normal force from the wall acts perpendicular to the surface of the wall and pushes the block away from the wall. This force is a reaction to the applied force that is pushing the block against the wall. It ensures that the block does not penetrate the wall and balances the component of the applied force that is perpendicular to the wall.

What role does friction play when a block is pushed against a wall?

Friction plays a crucial role in this scenario by opposing the motion of the block along the wall. If the block is pushed upwards or downwards, friction acts in the opposite direction to prevent or resist that motion. The frictional force is proportional to the normal force and depends on the coefficient of friction between the block and the wall.

How can the block remain stationary when pushed against the wall?

The block can remain stationary when the forces acting on it are balanced. This means that the applied force, normal force, gravitational force, and frictional force must sum to zero. Specifically, the frictional force must be equal and opposite to the component of the gravitational force parallel to the wall, and the normal force must balance the perpendicular component of the applied force.

What happens if the applied force is removed while the block is against the wall?

If the applied force is removed, the normal force from the wall will also disappear, as it is a reaction force. Without the normal force, there will be no frictional force to counteract the gravitational force. As a result, the block will no longer be held against the wall and will fall due to gravity.