Free Body Diagram of a Mass on a Slope
This freebody diagram shows the same forces that work on a slab of snow on a mountainside.
The slab has a mass of m. The slope has an angle of (alpha). The frictional force is (mu). The avalanche starts when ax > 0.
| F1 + F2 + F3 = m a (Newton's 2nd Law) | g = gravitational acceleration |
| F1 = force of gravity | acceleration in y direction: |
| F2 = normal force | ay = 0 |
| F3 = frictional force | |
| in x direction: | |
| m ax = F1x - F3 | |
| F1x = F1sin (alpha) | |
| F1 = m g | |
| F3 = (mu) m g cos (alpha) | |
| m ax = (m g sin (alpha)) - ((mu) m g cos (alpha)) | |
| ax = g (sin (alpha) - (mu) cos (alpha)) | |