Frictional force problem

In summary, the conversation is about finding the frictional force acting on a 16 kg mass that is at rest on an incline. The coefficients of static and kinetic friction, as well as the acceleration of gravity, are given. The process of finding the normal force and using it to calculate the static friction is mentioned, but the answer is still incorrect and the person is seeking help. The question also asks about the component of force down the incline and how much frictional force opposes it.
  • #1
kmikias
73
0
Hi all i have a question that i couldn't figure out here is the question.


1.A block is at rest on the incline. The coefficients of static and kinetic friction are μs = 0.7 and μk = 0.59, respectively. The acceleration of gravity is 9.8 m/s2 .What is the frictional force acting on the 16 kg mass? Answer in units of N

here is what i did.

First i try to find the normal force.which is F = M * a

which equall to N - cos33 * mg = ma
N - cos 33 * 16 (9.8) = 0 because acceleration is 0.
then N = 131.50

After i found normal force I use static friction = μ * N

which is 0.7 * 131.50 = 92.052.

Ok then my answer is still wrong so i need some help .

thank you.
 
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  • #2


What is the component of force down the incline? And therefore how much frictional force opposes it.
 
  • #3


Hello, thank you for your question. Based on your calculations, it seems like you are on the right track. However, there may be a small error in your calculations. The normal force should actually be equal to the weight of the block, which is 16 kg multiplied by the acceleration of gravity (9.8 m/s^2). This gives a normal force of 156.8 N.

Next, you can use the formula for static friction, which is μs * N, to calculate the maximum frictional force. In this case, it would be 0.7 * 156.8 = 109.76 N. This is the maximum amount of force that can be exerted by friction before the block starts to move.

Since the block is at rest, the frictional force acting on it would be equal to the force of gravity pulling it down the incline, which is mg * sin33. This gives a frictional force of 16 * 9.8 * sin33 = 82.15 N.

Therefore, the actual frictional force acting on the 16 kg mass is 82.15 N. I hope this helps to clarify the problem for you. Let me know if you have any further questions.
 

1. What is frictional force?

Frictional force is the resistance that occurs when two surfaces come into contact and try to slide against each other. It is caused by irregularities in the surfaces and the interlocking of microscopic bumps and grooves, which creates a force that opposes motion.

2. What are the different types of frictional force?

There are three main types of frictional force: static friction, kinetic friction, and rolling friction. Static friction occurs when two surfaces are not moving relative to each other, kinetic friction occurs when two surfaces are sliding against each other, and rolling friction occurs when one surface rolls over another.

3. How is frictional force calculated?

The amount of frictional force depends on the coefficient of friction between the two surfaces and the normal force pressing the surfaces together. The formula for calculating frictional force is Ff = μFn, where Ff is the frictional force, μ is the coefficient of friction, and Fn is the normal force.

4. How does frictional force affect motion?

Frictional force acts in the opposite direction of motion and can slow down or stop an object from moving. It also converts some of the kinetic energy of an object into heat, which is why surfaces may feel warm after rubbing against each other for a period of time.

5. How can frictional force be reduced?

Frictional force can be reduced by using lubricants, such as oil or grease, between two surfaces to reduce the amount of contact and friction. Smoother surfaces can also reduce frictional force, as well as decreasing the weight or normal force pressing the surfaces together.

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