PhysicsLAB Lab
Coefficient of Kinetic Friction (pulley, incline, block)

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The purpose of this experiment is to determine an unknown coefficient of kinetic friction between a wooden block and piece of shelving used as an incline plane using two photogates separated by a given distance, a known hanging mass, and a frictionless pulley system. Care needs to be taken that the string remains parallel to the surface of the incline.
 
 
During the experiment, the cart will initially start from rest. When the suspended mass is gently released, the cart, with its card of known length, will pass through each of the two photogates. The students will then be given the time required for the card to pass through each of the photogates. They need to also measure the distance between the photogates, the incline's angle of inclination, and record the mass of the hanging weight.
 
From this information they will be asked to show any freebody diagrams and the required calculations to determine the coefficient of kinetic friction between the block and the incline's top surface. A percent difference against the class average, since all groups used the same rquipment, will be the final evaluation.
 
 
Refer to the following information for the next five questions.

General Data
hanging mass in kilograms 

mass of sliding wooden block in kilograms 

distance between photogates in meters 

length of card in meters 

plane's angle of inclination in degrees 

Photogate Start Time End Time
#1
#2
 
 
Refer to the following information for the next two questions.

On your papers, draw two draw a freebody diagrams: one for the cart (m) and the other for the hanging mass (M). Then fill in the blanks provided with the generalized equations of motion for each object. Do not substitute in numerical values, you may use the variables: a, T, m, M, g, fk, and θ.
 
 
hanging mass' equation of motion 

sliding block's equation of motion 


Refer to the following information for the next four questions.

Now determine the average velocity of the cart as it passes through each of the photogates and then its average acceleration up the incline.
v1

v2

T = 

a = 

Refer to the following information for the next question.

Using your previously stated system of equations, solve for the coefficient of kinetic friction between the wooden block and the incline's surface. Show all of your calculations on your papers.
µk

Refer to the following information for the next question.

Once you have obtained your group's value µk calculate a percent difference based on averaging the data obtained from all groups.
your experiment's percent difference 



Your lab report should include your freebody diagrams and all of your calculations neatly organized and presented. Make sue that all numerical answers have appropriate units.

 
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