- #1

Carpetfizz

- 13

- 0

## Homework Statement

Just doing some practice problems from past finals and I needed some help on this one. Sorry if my question doesn't exactly fit the template.

**2) Relevant Equations / Information**

For part a) and for M_1, I drew the axes such that the x-axis points to the top right, in the direction of motion of M_1, and the y-axes points up perpendicular to it. For M_2 I drew the axes such that the x-axis points to the bottom right and the y-axis points up perpendicular to it.

This is the answer the solution guide provided

The difference is that my axes for M_1 was flipped such that the x-axis pointed in the opposite direction to what is presented in the solution.

I'm curious as to why they chose to make the direction opposite to M_1's motion positive.

**3) Attempt at Solution**

I tried doing it both ways and it yielded two different answers

1. The way in the answer sheet:

$$T = \frac{M_1M_2g(\mu_1cos(\phi)+sin(\phi)+sin(\theta)}{(M_1+M_2)}$$

2. The way with the different axis:

$$T = \frac{M_1M_2g(\mu_1cos(\phi)+sin(\phi)+sin(\theta)}{(M_1-M_2)}$$

I'm not exactly sure how switching the axes gives the right answer or what the rationale behind doing that is. Any advice would be much appreciated.