Calculating Kinetic Friction Coefficient with Object, Ruler and Book

[Jackpontikka]

My teacher gave us a homework. We must count the coefficient of kinetic friction between the object and the surface. We can only use the object, ruler and book or table etc. as the surface of motion. We are not allowed to count the acceleration with clock.

I decided to make the object slide by increasing the angle between book(the surface) and table. Finally object started sliding and I measured the angle($$\alpha$$). And finally I got: $$\mu$$= tan$$\alpha$$.

G_x = sin$$\alpha$$*G

Then I realized that the angle $$\alpha$$ is the angle when G_x>F_f0(read:the maximum of static friction)
But isn't F_f< F_f0.

So is this task even possible(without measuring the mass of the object or/and the acceleration) or what am I doing wrong?

P.S English isn't my first language! :)

 

[Stovebolt]

My teacher gave us a homework. We must count the coefficient of kinetic friction between the object and the surface. We can only use the object, ruler and book or table etc. as the surface of motion. We are not allowed to count the acceleration with clock.

I decided to make the object slide by increasing the angle between book(the surface) and table. Finally object started sliding and I measured the angle($$\alpha$$). And finally I got: $$\mu$$= tan$$\alpha$$.

G_x = sin$$\alpha$$*G

Then I realized that the angle $$\alpha$$ is the angle when G_x>F_f0(read:the maximum of static friction)
But isn't F_f< F_f0.

So is this task even possible(without measuring the mass of the object or/and the acceleration) or what am I doing wrong?

P.S English isn't my first language! :)

The task is possible with the items you have. You will not need the specific mass of the object as you are not looking for the specific frictional force.

Good job on finding the coefficient of static friction - you found the point by figuring out how to start motion. For kinetic friction, it may work better if you find out how to stop motion.

Depending on how you set things up, it may also help to consider the energy lost (or work done) in your experiment. Remember that potential energy = mass * acceleration (gravity) * height and that work = force * distance.

Keep working on it, you'll find a way to get the answer.

 

[thomate1]

I would first commend you for taking an active approach to solving this problem and using your resources creatively. However, I must point out that your method may not yield accurate results.

The coefficient of kinetic friction is defined as the ratio of the force of kinetic friction (Ff) to the normal force (Fn) between the object and the surface. It is a property of the materials in contact and does not depend on the angle of inclination or acceleration.

In your method, you are using the angle of inclination and the force of gravity (G) to calculate the coefficient of kinetic friction. However, this does not take into account the normal force, which is also a crucial factor in determining the coefficient of kinetic friction. Additionally, the maximum static friction force (Ff0) is not directly related to the kinetic friction force (Ff).

To accurately calculate the coefficient of kinetic friction, you would need to measure the mass of the object and the acceleration using a clock or other timing device. This would allow you to calculate the normal force and the kinetic friction force, from which you can then determine the coefficient of kinetic friction.

In conclusion, while your approach may yield a rough estimate of the coefficient of kinetic friction, it is not a reliable or accurate method. To obtain precise results, it is necessary to measure the mass and acceleration of the object.