1) In your lab notebook, draw a free-body diagram for the block+mass used in the
ID: 1899913 • Letter: 1
Question
1) In your lab notebook, draw a free-body diagram for the block+mass used in the first exploration and one for the block used in the second exploration. 2) For each of the two explorations, derive expressions for the static and kinetic coefficients of friction using any terms relevant to the situation (e.g., applied force, normal force, acceleration of gravity, mass, angle of incline). . Block Pulled on Flat Surface (a) Place a friction block fuzzy side down on a track and add some mass on top to give it extra traction. Pull the block VERY SLOWLY with a spring scale, starting with very little effort but continuously increasing your effort over a few seconds until the block suddenly slips, and then continuing for another second or two with the block sliding at constant speed. (b)Angle of Slip for Block on Inclined Plane Place a friction block (fuzzy side down) near one end of the track and slowly lift that end until the friction block slips. ANGLE=theta?????Explanation / Answer
A free-body diagram and a force analysis will yield the equation Ffrict = F|| for both the static and the kinetic situation. That is, when the object is at rest or moving down the incline at constant speed, the force down and parallel to the incline is balanced by the force which is up and parallel to the incline. The expressions for Ffrict and F|| can be substituted into this equation to yield µ•Fnorm = m•g•sin(theta) Knowing that Fnorm is equal in magnitude to Fperp, the expression for Fperp can be substituted into the equation for Fnorm. The new equation becomes µ•m•g•cos(theta) = m•g•sin(theta) The angles for both the static and the kinetic case are known and mu (coefficient of friction) is the unknown. So the equation can be re-arranged to µ = m•g•sin(theta)/m•g•cos(theta) The mass (m) and the acceleration of gravity (g) cancel from both the numerator and the denominator leaving sin(theta)/cos(theta) on the right side. This can be simplified again to µ = tan(theta)
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