# Math Help - A 42.0 kg block of ice

1. ## A 42.0 kg block of ice

A 42.0 kg block of ice slide down a plane with an incline of 34 degree assuming friction is negligible, what is the acceleration of the block down the incline?

2. Originally Posted by Refujoi
A 42.0 kg block of ice slide down a plane with an incline of 34 degree assuming friction is negligible, what is the acceleration of the block down the incline?
Set up your Free-Body Diagram. I am going to assume the incline is down and to the right. For a coordinate system I am going to say that +x is down the incline and +y is perpendicular to and coming out of the plane of the incline.

There are two forces in the FBD: the weight, w, acting straight downward, and the normal force, N, acting in the +y direction.

The only force having a component in the x direction is the weight, so:
$\sum F_x = w sin \theta = ma$
where $\theta$ is the angle of incline. (Note that it is not cosine!)

Since w = mg we may solve this equation for a and we get
$a = g sin( \theta )$.

(Note that the acceleration is less than g as it should be.)

-Dan