Physics - Inclined Plane - Experimental Investigation

[Christine L]

Homework Statement

A wooden box is at rest on a ramp inclined at an angle Ө to the horizontal. W is the weight of the box and its contents. A frictional force prevents the box sliding down the ramp. A reaction force acts on the box perpendicular to the inclined plane. The inclined plane is hinged at its lower end so that it can be easily lifted to alter the angle Ө.

Describe how you would investigate the relationship between W and the angle, Өs, at which the box just starts to slide down the ramp.

Image is attached.

Homework Equations

I don't feel equations are need, except perhaps possibly the resolved components of W. These being mgsinӨ (the component of weight parallel to the slope), and mgcosӨ (the component of weight perpendicular to the slope). Very unlikely that F = µR will be needed.

The Attempt at a Solution

I've been told I need to consider the following:

• What measurements do I need to take (i.e. what are my x and y variables)?
• What measuring instruments shall I require to make these measurements?
• State an appropriate range and interval for my independent axis.
• Plot a graph of y variable against x variable.
• Conclude what the results would look like, and what they represent/theorise.

I think my independent variable is Ө, and I could measure this using a protractor. I could use intervals of 10°, and take a range of 10° to 80°.

My main problem is not being sure what my dependent variable would be, as without knowing that I can't state what my plotted graph would be or even begin to think what it would look like plotted and theorise.

Help would be appreciated!

Thanks!

 

[Simon Bridge]

Don't worry about that ... start out be describing the experiment.

Aim:
"to find the relationship between the weight of the box and the maximum angle that static friction will hold it."

Theory:
this is where your equations go - use your physics knowledge to predict the relationship that you are trying to find.

Method:
describe how you are going to do the experiment.

Results:
just a table of your measurements

Analysis:
Here is where your graph goes ... by convention, the variable under your control goes on the horizontal axis. In physics we just use whatever makes the math easy.

It is a good idea to change things so that the graph is a line, then you can use the slope of the line as support (or otherwise) for the theory. i.e. your theory relationship may be θ=g√W ... if you plot θ vs W you will get a curve ... but if you plot θ vs √W you will get a line. If the theory is right, then the slope of the line should be close to the value of g in the theory. Much more useful.

*** Right to this point is what you need to figure out to get full marks.

Conclusion:
This is where you rewrite the "aim" as the answer to a question and tack on what you found out.

 

[Basic_Physics]

The independ variable is the total weight of the box, which you should change during the course of the experiment. The dependent variable is the angle at which sliding starts. According to the theory the angle does not depend on the weight.

 

[Simon Bridge]

Part of the exercise is to think your way through the experiment though ... I had hoped OP would be able to figure that out without having to be told quite so directly. Ho hum.

 

[Nickie]

I would approach this experiment by first setting up the inclined plane and wooden box as described. I would then vary the angle Ө, starting from 10° and increasing by 10° intervals up to 80°. At each angle, I would measure the weight of the box and its contents using a scale, and record this as my dependent variable. My independent variable would be the angle Ө, which I would measure using a protractor.

Based on the given information, I would expect to see a linear relationship between the weight of the box and the angle Ө. This can be represented by the equation W = mgsinӨ, where m is the mass of the box and g is the acceleration due to gravity. As the angle increases, the component of the weight parallel to the slope (mgsinӨ) also increases, until it reaches a critical angle where the weight is just enough to overcome the frictional force and cause the box to slide down the ramp. This critical angle would be the angle at which the box just starts to slide down the ramp, and can be determined by plotting a graph of weight (dependent variable) against angle (independent variable).

In order to accurately measure the weight and angle, I would use a scale with a high precision and a protractor with clear markings. I would also repeat the experiment multiple times at each angle and take an average to reduce any errors. Additionally, to ensure that the frictional force remains constant, I would use the same ramp and box for each trial and check for any wear and tear on the surfaces.

In conclusion, by systematically varying the angle Ө and measuring the weight of the box at each angle, I would be able to investigate the relationship between weight and angle and determine the critical angle at which the box just starts to slide down the ramp. This experiment would provide valuable insights into the forces acting on objects on inclined planes and could be further extended by investigating the effects of different surface materials or varying the weight of the box.