# Newton's Laws Test Problem

#### giantfetus

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.

Thanks!

Edit: Fixed image attachment.

Last edited:

#### giantfetus

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.

Thanks!

The image is quite large, so sorry about that!

#### Woody

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)

#### ChipB

PHF Helper
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