# Mass on a moving wedge

#### bigevil

1. Homework Statement This is a frictionless system with the wedge on a frictionless horizontal surface. When the system is released, the horizontal wedge (mass M) with diagonal angle theta moves to the left with constant acceleration a. What is it?

I hope I'm right when I say this is not a very easy question, because I spent ages on it but I'm still not sure what the answer is. Can someone please help me check the answer?

2. Homework Equations

The mass (=m) does not leave the wedge. Taking the perpendicular component of the wedge's acceleration,

$$ma sin \theta = mg cos \theta - N$$ where N is the normal reaction force between the wedge and the mass, directed perpendicular to the plane.

Applying Newton's second law, the horizontal acceleration on the wedge is solely created by the normal force. Therefore $$Ma = N sin \theta$$. Then applying algebra,

$$a = \frac{mg sin\theta cos\theta}{M + m {sin}^2 \theta}$$.

Related Introductory Physics Homework Help News on Phys.org

#### thepopasmurf

I think you have your answer. No values have been given for any of the variables so the best you can get is an expression for a.

Edit: I just worked it out myself and I got the same expression for a as you

Last edited:

#### bigevil

All right... thanks :)

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving