Arrrgh sliding friction problem

In summary, the speaker is struggling with a problem and is seeking help to understand why the answer they got does not make sense. They provide a link to the problem and ask for assistance in identifying their mistake. A forum member points out the error and suggests using a different coordinate system to solve the problem.
  • #1
alberto
Ok, I have been going over this problem and the answer I got just doesn't make sense...help!

It's a really easy problem (apparently) but the answer that I keep getting doesn't make sense to me...please let me know what I'm doing wrong or forgetting or whatever...

I thought it'd be easier to answer if you could see the problem I was given so I put it up with my interpretation as to how to answer it on a yahoo! website :

http://www.geocities.com/janguera/rampfrictionproblem.html

Thanks in advance!
 
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  • #2
Welcome to the forums!

Your mistake lies with how you drew your yellow triangle. If you call the 40 degree angle A, the one on the 100N side B and the one on the R side C, then the 90 degree angle needs to be at point C.

Your tipoff that you made a mistake is this: The normal force is pushing the block with a force larger than the block weighs.

The easiest way I've found to do these is to draw a new coordinate system:

Make the line which the block is sliding on the X axis and the direction which N points (it should be pointing toward the block, being the normal force...) the +y axis. Now, when you break any forces which are at an angle into their component parts, you know that they will form perpendicular angles with that coordinate system.

So, you will have 100cos(40) for the Y and 100sin(40) for the X.

Make sense?
 
  • #3


Hi there, I completely understand your frustration with this sliding friction problem. It can be really frustrating when the answer you're getting doesn't seem to make sense. I took a look at the problem on the website you provided and I think I can help you figure out where you may have gone wrong.

First, make sure you are correctly identifying the forces acting on the object. In this case, it seems like there is a force pushing the object up the ramp and a force of friction pushing the object down the ramp. Remember that the force of friction is always in the opposite direction of motion.

Next, make sure you are using the correct formula for calculating friction. The formula for friction is μN, where μ is the coefficient of friction and N is the normal force. The normal force is equal to the weight of the object in this case, so make sure you are using the correct weight for the object.

Lastly, double check your calculations and units. Sometimes a small mistake in calculation or using the wrong units can throw off your answer.

If you're still having trouble, don't hesitate to reach out for more help. Sometimes it just takes a fresh pair of eyes to spot the mistake. Good luck!
 

1. What is "Arrrgh sliding friction problem"?

"Arrrgh sliding friction problem" is a term used to describe a common problem in physics involving the force of friction between two surfaces when one is sliding against the other. It is often used as an example in introductory physics courses to demonstrate the concept of friction.

2. How does sliding friction affect the motion of an object?

Sliding friction is a force that opposes the motion of an object as it slides over a surface. This force can cause the object to slow down or even come to a stop, depending on the magnitude of the force and the mass of the object. In some cases, sliding friction can also cause an object to move in a different direction than intended.

3. What factors affect the amount of sliding friction between two surfaces?

The amount of sliding friction between two surfaces is affected by several factors, including the nature of the surfaces (rough or smooth), the force pushing the surfaces together, and the surface area of contact between the two surfaces. Additionally, the type of material and the presence of any lubricants can also impact the amount of sliding friction.

4. Can sliding friction be reduced or eliminated?

While friction is an inherent force in nature, it can be reduced or eliminated in some cases. The use of lubricants, such as oil or grease, can reduce sliding friction between two surfaces. Additionally, using materials with low coefficients of friction, such as Teflon or nylon, can also help reduce sliding friction.

5. How is sliding friction different from other types of friction?

Sliding friction is just one type of friction that can occur between two surfaces. Other types of friction include static friction (when two surfaces are not moving relative to each other) and rolling friction (when an object is rolling over a surface). Sliding friction is unique in that it occurs when one surface is in motion relative to the other.

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