# How to find Coeff of kinetic friction without mass?

• pierce_E
In summary, a student is seeking help with a physics lab that requires them to devise a procedure for measuring the coefficient of kinetic friction between a block and a table using limited equipment. They are also asked to derive an expression for the coefficient of friction in terms of gravity and the measured quantities. The student is unsure of how to approach the problem and the guidelines on the forum require them to show their attempt before seeking assistance.
pierce_E

## Homework Statement

For my Physics lab this is what my teacher handed me... I have no idea how to attack the situation, can someone help solve?
Devise a procedure for an experiment which will measure the coefficient of kinetic friction between a block of unknown mass m and the table, where the only equipment which can be used is the following:
1) A string of negligible mass
2) two blocks of unknown identical masses which are able to be attached to string
3) a pulley
4) measuring tape(s)
Derive an expression for the coefficient of friction between the table and the block in terms of g and quantities measured with the equipment above.

## The Attempt at a Solution

Hello Pierce,

First post on PF and you bump into a culture issue: the guidelines require an attempt on your part.
List the equations that you think are relevant,
Describe some experiments that would help you determine relevant variables, etc.

And don't worry: mass might well divide away and thus drop out of the calculations.

## 1. What is the formula for calculating coefficient of kinetic friction without mass?

The formula for calculating coefficient of kinetic friction without mass is μ = Fk/N, where μ is the coefficient of kinetic friction, Fk is the force of kinetic friction, and N is the normal force.

## 2. How do I measure the force of kinetic friction?

The force of kinetic friction can be measured by using a spring scale to pull an object along a surface at a constant speed. The reading on the spring scale at this speed will be equal to the force of kinetic friction.

## 3. What is the normal force and how do I calculate it?

The normal force is the force exerted by a surface on an object that is in contact with it. It is perpendicular to the surface and prevents objects from passing through each other. It can be calculated by multiplying the mass of the object by the acceleration due to gravity (9.8 m/s2).

## 4. Can coefficient of kinetic friction be negative?

No, the coefficient of kinetic friction cannot be negative. It is a measure of the amount of friction between two surfaces and is always a positive value.

## 5. How can I use the coefficient of kinetic friction to predict the motion of an object?

The coefficient of kinetic friction can be used to predict the motion of an object by calculating the net force acting on the object and using the equation F = ma (force = mass x acceleration). If the net force is greater than the force of kinetic friction, the object will accelerate. If the net force is equal to the force of kinetic friction, the object will move at a constant speed. If the net force is less than the force of kinetic friction, the object will decelerate.

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