How do I find the the coefficient for kinetic friction given

• bgt
In summary, the conversation is about finding the coefficient for kinetic force of a 10.0 kg box on a horizontal board raised at an angle of 13.9° with the floor. The box is initially sliding at a constant velocity when the board is raised at an angle of 12.8°. The conversation includes the use of a free-body diagram and determining the forces acting on the box, including normal force, friction force, and gravity. The acceleration of the box is zero as it is sliding at a constant speed and direction.
bgt
A 10.0 kg box rest on a horizontal board. One end of the board is slowly raised to 12.8° with the floor, the box slides at a constant velocity. (Use this information to find the kinetic coefficient). Find the magnitude and direction of the acceleration of the box when the board is raised to an angle of 13.9° with the floor.

2. I am absolutely STUCK at finding the coefficient for kinetic force, especially with the given information.3. mg⋅cos12.8-10kg⋅2.35m/s^2 divided by 98N (mg)
2.35m/s^2 being acceleration (=(gravity)sin).

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bgt said:
A 10.0 kg box rest on a horizontal board. One end of the board is slowly raised to 12.8° with the floor, the box slides at a constant velocity. (Use this information to find the kinetic coefficient). Find the magnitude and direction of the acceleration of the box when the board is raised to an angle of 13.9° with the floor.

2. I am absolutely STUCK at finding the coefficient for kinetic force, especially with the given information.3. mg⋅cos12.8-10kg⋅2.35m/s^2 divided by 98N (mg)
2.35m/s^2 being acceleration (=(gravity)sin).
Welcome to the PF.

There is a classic relation between the angle of the incline where the mass starts sliding and the coefficient of friction. Do you know what that is? If not, please look in your textbook or use Google to help you get past that step...

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Thanks-I've been doing that and keep getting directed back here...

bgt said:
A 10.0 kg box rest on a horizontal board. One end of the board is slowly raised to 12.8° with the floor, the box slides at a constant velocity. (Use this information to find the kinetic coefficient). Find the magnitude and direction of the acceleration of the box when the board is raised to an angle of 13.9° with the floor.

2. I am absolutely STUCK at finding the coefficient for kinetic force, especially with the given information.3. mg⋅cos12.8-10kg⋅2.35m/s^2 divided by 98N (mg)
2.35m/s^2 being acceleration (=(gravity)sin).
When in doubt, start with a free body diagram. What forces act on the 10.0 kg box?

jbriggs444 said:
When in doubt, start with a free body diagram. What forces act on the 10.0 kg box?

Thanks for the response.

Normal force, friction, gravity and mass. I was just SUPER confused at getting to the coefficient for friction. I did draw a free-body diagram. This is my very first time taking physics and I am really struggling with it.

bgt said:
Normal force, friction, gravity and mass. I was just SUPER confused at getting to the coefficient for friction. I did draw a free-body diagram. This is my very first time taking physics and I am really struggling with it.
Only three of those things are forces. Which three?

jbriggs444 said:
Only three of those things are forces. Which three?
Normal force, friction force and gravity. I know that normal force is perpendicular, gravity is straight down and friction goes against the object. I struggle with setting up the equations.

bgt said:
Normal force, friction force and gravity. I know that normal force is perpendicular, gravity is straight down and friction goes against the object. I struggle with setting up the equations.
The block is sliding at a constant speed in a constant direction. What is its acceleration?

1. How do I calculate the coefficient of kinetic friction?

To calculate the coefficient of kinetic friction, you need to divide the force of kinetic friction by the normal force acting on the object. The force of kinetic friction can be found by multiplying the coefficient of kinetic friction by the normal force.

2. What is the formula for finding the coefficient of kinetic friction?

The formula for finding the coefficient of kinetic friction is μk = Fk / N, where μk is the coefficient of kinetic friction, Fk is the force of kinetic friction, and N is the normal force.

3. How do I measure the force of kinetic friction?

The force of kinetic friction can be measured by using a spring scale or a force sensor. Attach the scale or sensor to the object and pull it along the surface with a constant velocity. The reading on the scale or sensor will be the force of kinetic friction.

4. What factors affect the coefficient of kinetic friction?

The coefficient of kinetic friction is affected by the types of surfaces in contact, the roughness of the surfaces, and the normal force acting on the object. It also depends on the temperature and the presence of any lubricants between the surfaces.

5. Can the coefficient of kinetic friction be greater than 1?

Yes, the coefficient of kinetic friction can be greater than 1. This occurs when the force of kinetic friction is greater than the normal force, resulting in a coefficient value greater than 1. This is often seen in situations where there is a lot of friction, such as rubber on concrete or sandpaper on wood.

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