- #1

Alex126

- 84

- 5

## Homework Statement

There is a mass

**m**on an incline (angle

_{1}**α**), connected to a pulley with a string, and on the other side of the pulley, after another string, there is a mass

**m**. See picture if it's unclear, I'm not sure how to express the problem.

_{2}Anyway the plane has a friction coefficient

**μ**.

Need to find the Tension

**T**of the string and the acceleration

**a**of the system. Pretty sure I know how to solve the general problem, but I have an issue with the Friction Force.

## Homework Equations

F = m*a

Friction = μ * Normal force

## The Attempt at a Solution

As I said, my main problem is with the Friction Force. In particular, I don't know whether I should calculate the Normal force as the first or the second option:

1. Normal Force = Weight Force 1 * cos (α)

2. Normal Force = Weight Force 1 * cos (α) + Weight Force 2

In other words, I don't know if I should include the Weight Force 2. My first thought was to include only the first object, since it's the only one directly in contact with the plane, but since the second mass is also indirectly connected with the plane through the strings and the first object, I wonder if it should be included too.

Once that's found, the problem should be solved with F = m*a. So I would do:

(assume motion down the plane)

+Weight Force 1_x - Friction - Weight Force 2 = (m

_{1}+m

_{2}) * a

(Weight Force 1_x = m

_{1}* g * sin (α))

That gives

**a**.

Then, focusing on the second body:

+Tension - Weight Force 2 = m

_{2}*a

That gives

**T**.