Newton's Laws Test Problem

Oct 2018
Baltimore, MD
So I'm taking a practice test for an upcoming exam, and this problem has me stumped. I've attached an image here, as you can see I have some equations written out. My problem now is that I'm left with 3 unknowns (normal force, acceleration in x, and angle theta).

Anyone wanna toss me in the right direction here? First post btw, probably gonna be a few more after this judging by how this class is going so far.


Edit: Fixed image attachment.

Last edited:
Oct 2018
Baltimore, MD
Not sure what happened to my post, it kind of vanished after editing.

Basically, I have this problem (image attached) and I'm stuck. I have these 2 equations but I have 3 unknowns (normal force, acceleration in x, and angle theta).

If anyone could toss me in the right direction I would greatly appreciate it.


The image is quite large, so sorry about that!

Jun 2016
My current computer setup will not allow me to view the posted image,
however the brief description you give sounds very much like a basic trigonometry problem.

The Force in X is related to the Normal force via the angle Theta
XForce = NForce * SIN(Theta)


PHF Helper
Jun 2010
Morristown, NJ USA
You're not too far away from being able to answer (2). You have figured out that F_y = 0, you have an expression for F_n, and you almost have F_x (you actually have written acceleration in the x-direction; the force F_x is acceleration times mass). So - first off, what's the total force, F_net? You could use |F_net| = sqrt(|F_x|^2 +|F_y|^2), but given that F_y=0 it should be pretty obvious what F_net is. Then, use simple trig to determine the angle theta if |F_n|/|F_net| = 0.554