Friction - minimum value of force for movement

[voliseq]

Homework Statement

Determine the minimum value of the force F for which the systems start moving. Assume M1 = 1kg, M2 = 2kg, Us = 0.3.
Solution: F = 9; F = 6N

My problem is that i don't know the forces acting on wheel.

Homework Equations

The Attempt at a Solution

M1 :
F - T = 0
M1g - N = 0
M2:
Fr - T = 0
M1g+M2g - N(from mass 1 and mass 2) = 0

 

[SammyS]

Homework Statement

Determine the minimum value of the force F for which the systems start moving. Assume M1 = 1kg, M2 = 2kg, Us = 0.3.
Solution: F = 9; F = 6N

My problem is that i don't know the forces acting on wheel.

Homework Equations

The Attempt at a Solution

M1 :
F - T = 0
M1g - N = 0
M2:
Fr - T = 0
M1g+M2g - N(from mass 1 and mass 2) = 0

Hello voliseq. Welcome to PF !

Which wheel (or wheels) ?

 

[voliseq]

Hi Sammy, i mean those wheels attached to M1 (on first picture) and M2(on second picture).

 

[Chestermiller]

Hi Sammy, i mean those wheels attached to M1 (on first picture) and M2(on second picture).

The only forces acting on the wheels are normal (vertical) forces. The wheels are free to rotate, so the horizontal forces acting on them are zero.

Chet

 

[voliseq]

Another problem

Thanks Chest it works, now i have got another problem to solve,
1. Here is the problem

2. And here is my attempt at solution

I think something is wrong here as i can't get correct result

 

[Chestermiller]

The members AB and BC need to be in equilibrium. In terms of P, what is the normal force exerted by the cylinder on AB? What is the normal force exerted by AB on the cylinder?

Chet

 

[voliseq]

The members AB and BC need to be in equilibrium. In terms of P, what is the normal force exerted by the cylinder on AB? What is the normal force exerted by AB on the cylinder?

Chet

N = Pcos30 ?

 

[Chestermiller]

N = Pcos30 ?

Please try again, taking moments about the pin.

Chet