Lab 7 –Testing Static and Kinetic Friction Forces:
The objective of this lab to determine the coefficients of static friction and kinetic friction between different surfaces. You will be pulling with increasing tension until the object begins to slide and then you will keep the object moving at a slow steady speed. The graph below the action is a graph of the tension in the string.
When you are ready to start the experiment, click on the begin button. http:
www.thephysicsaviary.com/Physics/Programs/Labs/ForceFriction
The screen will look like this:
Steps:
· Draw Free Body Diagram of the setup when object is not moving and then when it is ready to move.
· Pick a mass of the object and one type of surface and record them. Mass (M) = ____________ kg, Surface type = _____________.
· Then click to start and keep observing force applied in lab quest.
· When object shows a kink means ready to move, check value of force, that is the force when it is equal to static friction force. It is the maximum value of force that appears in the screen and graph as maximum value of force. Record its value from graph. Fs (static max) = ________ N
· Keep looking the lab quest and see when the value of force drops from its maximum value, record that value and it would be equal to kinetic friction force when object is moving with constant speed. This value you can see in the graph as a flat line. Record that value of Force from graph which is Fk (kinetic force) = ___________ N.
· Now using FBD, find out value of coefficient of static friction force from Fs and write down here. Use this equation (Fs = μs * M*g) to find μs = ______________.
· Then calculate from FBD the value of coefficient of kinetic friction and write down here. Use this equation (Fk = μk * M*g) to find μk = _______________.
· Repeat steps from 2 to 7 for other four types of surfaces keeping same mass of the object and record all values of forces and coefficients in the form of a table and compare which surface gives more static friction/kinetic friction and which least.
· Repeat steps from 2-8 for one type of surface but five different masses of the object and show your all finding in the form of a table.
· Write a conclusion what you learned from here and what the difference between static and kinetic friction forces.
https:
en.wikibooks.org/wiki/Physics_Study_Guide/Frictional_coefficients
https:
www.engineeringtoolbox.com/friction-coefficients-d_778.html