Force of block pushed against wall

In summary, the conversation is about a block of mass 20 kg being pushed against a vertical surface with a coefficient of friction of 0.2. The question asks for the minimum magnitude of force P needed to keep the block still when θ = 30°. The equations for x and y were derived using a force body diagram, and the attempt at a solution involved substituting the value for force of friction into the y equation. The questioner is stuck because they do not know the acceleration. The problem is asking for the minimum magnitude of P needed to hold the block still, and it is unclear what type of friction is involved.
  • #1
uph0
3
0

Homework Statement


A block of mass 20 kg is pushed against a vertical surface (see picture). The coefficient of friction, μ, between the surface and the block is 0.2. If θ = 30°, what is the minimum magnitude of P to hold the block still?
8068667509_7a94fd1fa4.jpg


Homework Equations



f = force of friction = μN

The Attempt at a Solution


I drew a force body diagram and got equations for x and y.
x: N - Psinθ = 0
Y: -pcosθ + mg + f = may

N = psinθ
so f = μ psinθ
I put f = μ psinθ into the y equation

so i get
-pcosθ + mg + μpsinθ = may

I'm stuck here. I want to find P but I don't know the acceleration.
 
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  • #2
The problem states that the block is still, which would mean that ay = ?
 
  • #3
uph0 said:
I'm stuck here. I want to find P but I don't know the acceleration.
The question asks:
what is the minimum magnitude of P to hold the block still?
Therefore the magnitude of the velocity is...?
The change in velocity is ...?
The acceleration is ...?

Why "minimum"? What kind of friction is this?
 

What is the force of a block pushed against a wall?

The force of a block pushed against a wall is the amount of energy that is exerted on the wall by the block. It is measured in units of Newtons (N).

How is the force of a block pushed against a wall calculated?

The force of a block pushed against a wall can be calculated using the formula F=ma, where F is the force, m is the mass of the block, and a is the acceleration of the block. Alternatively, it can also be calculated using the formula F=P/A, where P is the pressure applied to the wall and A is the area of contact between the block and the wall.

Does the force of a block pushed against a wall depend on the mass of the block?

Yes, the force of a block pushed against a wall is directly proportional to the mass of the block. This means that as the mass of the block increases, the force exerted on the wall also increases.

What factors can affect the force of a block pushed against a wall?

The force of a block pushed against a wall can be affected by the mass of the block, the acceleration of the block, the surface of the wall, and the angle at which the block is pushed against the wall.

Can the force of a block pushed against a wall be greater than the force applied to the block?

Yes, it is possible for the force of a block pushed against a wall to be greater than the force applied to the block. This is because the wall can exert an equal and opposite force on the block, resulting in a greater overall force on the wall.

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