# Can someone help me with this static friction problem?

• shaggyace
In summary, the coefficient of static friction between the crate and inclined ramp was incorrectly calculated due to the use of incorrect values for the weight and the angle. Once the correct values were used, the coefficient of static friction was found to be 2.13.
shaggyace

## Homework Statement

A 45-kg crate is placed on an inclined ramp. When the angle the ramp makes with the horizontal is increased to 24 degrees , the crate begins to slide downward. What is the coefficient of static friction between the crate and the ramp?

## Homework Equations

$\Sigma$F=ma

fs=$\mu$sN

## The Attempt at a Solution

I started by drawing a free body diagram. My weight came out to be -441 N. I have the angle of my weight at 24 degrees. The normal force at mgcos24, for which I got 187N. mgsin24 came out to be 399N which is also the static friction force. Then I just substituted into the static friction equation and my coefficient of static friction came out to be 2.13. I entered this into the homework problem which we do online and it is wrong. Did I miss a step? What did I do wrong?

The applied formula is right.The math is wrong.

the weight u calculated using m as 450 and g as 9.8 (all in SI units) is right as 441 N.

As u said normal force is mgcos24.
and mgsin24 as component of weight parallel to inclined plane.However, the calculated values are not right.

Hint(for angles less than 45 degrees cos x is always greater the sin x.

However, here your mgcos24 is less than mgsin24)

Last edited:
Wow, thanks a lot Calc class, lol.

As a scientist, it is important to carefully analyze the problem and double check your calculations. It seems that you have made a mistake in your calculation for the normal force. The correct value should be 408 N, which would result in a coefficient of static friction of approximately 0.49. It is also important to check the units of your answer to make sure they are consistent with the expected units for a coefficient of friction. In this case, the units should be unitless. I would recommend checking your calculations and trying again to see if you get the correct answer. If you continue to have trouble, it may be helpful to seek assistance from a classmate, teacher, or tutor.

## 1. What is static friction?

Static friction is a force that opposes the motion of an object when it is in contact with another surface. It is caused by the microscopic irregularities between the two surfaces that prevent them from sliding past each other.

## 2. How do you calculate static friction?

The formula for calculating static friction is μsN, where μs is the coefficient of static friction and N is the normal force acting on the object.

## 3. What factors affect static friction?

The coefficient of static friction depends on the nature of the two surfaces in contact, their roughness, and the force pressing them together. It also increases with the surface area in contact and decreases with the force applied parallel to the surface.

## 4. Can static friction be greater than kinetic friction?

Yes, static friction can be greater than kinetic friction. This is because static friction is the maximum force that can be applied before an object starts to move, while kinetic friction is the force that opposes the motion of an already moving object.

## 5. How can I reduce static friction?

To reduce static friction, you can use lubricants between the two surfaces in contact. This will reduce the roughness and allow the surfaces to slide past each other more easily. You can also decrease the force pressing the surfaces together or increase the surface area in contact.

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