16-March- Modeling Friction Forces

Calculating Coefficients of Static and Kinetic Friction

Purpose

We want to calculate the Static and Kinetic frictional values for a block using different techniques

Part 1

For the first part, we placed a block of wood on a table and attached a string to it and placed a cup on the other end. We gradually filled the cup with water until the block broke free and started to move. we recorded the mass of the cup with water and repeated this 4 times while adding a block each time.

 The picture above shows how we preformed the experiment and the data below shows what was collected of the masses of both the cup and the blocks that were used to achieve maximum static friction. We found our coefficient to be 0.260.

Part 2

For the second part, we attached the block to a force sensor and used logger pro to record the amount of force needed to pull the block at constant speed across the same surface. This was repeated 4 times while adding a block after each trial

The two pictures above show the first and last trial where the blocks were hooked up to the force sensor and pulled at constant speed. 

Above is the data that was recorded and the coefficient friction we obtained was 0.313, which was higher than out static coefficient 

Part 3/4

For the final two parts, we put them together and achieved only the answer to coefficient of kinetic friction. We calculated that the static coefficient at an angle would be equal to the tangent of the angle but we never actually proved this. Instead we continue on to part 4 and used a motion sensor to find the acceleration and calculate the kinetic coefficient at various angles

The picture above shows how the experiment was performed. A hanging mass that was

 just heavy enough to accelerate the block up the ramp was used and 

the motion sensor recorded the acceleration. 

We used kinematics to solve for the kinetic coefficient of 0.234.

Our calculated value was very similar with a value of 0.227

Conclusion

I believe the methods we used to calculate the static coefficient on the table and incline were accurate but the methods to find the kinetic coefficient seemed to be all over the place and a reliable number could not be achieved. Especially when the block had to be pulled at a constant speed. This was difficult to replicate every time.