Homework Help: Need to determine an angle depending on acceleration

1. Oct 6, 2004

Hi guys. We did an experience on an inclined plan and I got this acceleration: -0,324 m/s2 . Now all I know is this:

the mass of the object was 552g. g = -9,8 m/s2 and I need to find out what was the angle of the plane. I have to give this tomorrow so I need help on this please.. the teacher gave us a hint with this -gsinx but if I use that it gives me an angle of less than 2degrees.
Can somebody help me on this easy question please?

2. Oct 6, 2004

Pyrrhus

If the inclined plane was frictionless, then the acceleration the object will experiment will be -gsin(x).

3. Oct 6, 2004

Diane_

You can always tell when people hit vectors in physics. :)

Make a sketch of your inclined plane. What you're trying to do is decompose the vectors into those parallel to and those perpendicular to the plane - which is where your teacher's hint comes in.

If you simply assume that the acceleration was "g sin(x)", then you're assuming that the plane was frictionless. Perhaps this is what was intended, but that seems unlikely to me. You probably need to factor in friction. If this was intended (which would explain why you have the mass), then you'll need a "coefficient of friction" for the plane.

Without knowing more details about your experiment and the point of it, I can't really say anything else. For what it's worth, I get 1.9 degrees ignoring friction.

4. Oct 6, 2004

So I was right about the little angle.. but it seems too small. Thanks!

5. Oct 6, 2004

Pyrrhus

I agree Diane, hehehe, as you can see Physics I course it's a shock for most students, i remember when i took Physics I, i had to change my way of solving problems, but in the end it prepared me for the other advanced subjects of my career such as Static, Dynamics, etc..

6. Oct 6, 2004

Gokul43201

Staff Emeritus
The frictionless calculation tells you a lower limit on the angle.

To get the actual angle, you need, as Diane and cyclo have suggested, to know the force of friction between the block and the incline. To determine the friction between the surfaces you need more data...meaning you could have done more experiments to figure this out. Did you ?

7. Oct 6, 2004