Forces & Motion 5: Block Pushed Against Wall - Will it Move?

In summary, the block with a weight of 5N is being pushed by a 12N force against a vertical wall. The coefficient of static friction between the wall and the block is .60 and the coefficient of kinetic friction is .40. Based on the forces applied, the block will not start moving. The force exerted on the block by the wall is 12N in the direction of the normal reaction and the frictional force.
  • #1
theunloved
43
1
5. A 12N horizontal force F vector pushes a block weighing 5N against a vertical wall. The coefficient of static friction between the wall and the block is .60 and the coefficient of kinetic friction is .40. Assume the block is not moving initially.
(A) will the block start moving?
(B) What is the force exerted on the block by the wall?

I draw a FBD on the block, and these are all the forces that I've found:
Take y upwards and x positive going from left to right

y direction:
-mg - fs = 0
fs = -mg = -5N

x direction
F - Fc (contact) = 0
F = Fc = 12N

Part a.
The maximum static friction that prevents the block from moving down is
fs = 0.6 * 12 = 7.2 N
since magnitude of fs > magnitude of mg, the block will not move.

Part b:
From x direction, we have F = Fc = 12N, so the force on the block from the wall is vector Fc = (-12N)i


Did I do it right ? Did I miss any forces on my FBD ?
 
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  • #2
hi first part seems ok. the sign of [itex]f_s[/itex] should be positive though.
for the second part, wall exerts force in two different directions. one is normal reaction
as you pointed out and the frictional force which is upward...so you will need to find the
magnitude and angle of the resultant force
 

FAQ: Forces & Motion 5: Block Pushed Against Wall - Will it Move?

How does the force of the block affect its motion against the wall?

The force of the block determines how much it will move against the wall. If the force is greater than the frictional force between the block and the wall, the block will move.

What is the relationship between the block's mass and its acceleration?

According to Newton's Second Law of Motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This means that the greater the mass of the block, the slower its acceleration will be.

Will the block ever reach a constant velocity when pushed against the wall?

No, the block will not reach a constant velocity when pushed against the wall. This is because the block will continue to experience a force from the wall, causing its velocity to constantly change.

How does the angle at which the block is pushed affect its motion?

The angle at which the block is pushed will affect the direction of its motion. If the block is pushed at an angle perpendicular to the wall, it will move directly towards or away from the wall. If the block is pushed at an angle parallel to the wall, it will slide along the wall.

Is there a maximum amount of force that can be applied to the block without it moving?

Yes, there is a maximum amount of force that can be applied to the block without it moving. This is known as the static frictional force, and it is equal to the force applied to the block as long as it is less than or equal to the coefficient of static friction multiplied by the normal force between the block and the wall.

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