Testing Coefficients of FrictionQuestion:
1)will U(k) or U(s) be influenced by the weight of the object?2)will U(k) or U(s) be influenced by the angle of the ramp?Hypothesis:
U(k)and U(s) are determined by the surfaces of the two objects. The friction force is directly proportional to the normal force ofthe object.Materials :
a wood object that has 3 spaces for weights 45g3 weights 50geachseveral small weights /a plastic cup /
desk that surface made of wood /spring scale scales 2.5NTheory:
The friction force is directly proportional to the normal force of the object F(f)=U*f(N)Procedure:
(1)As show in figure below: Firstly ,test the Kinetic coefficient of friction. Put a 50g weight on the wood object, then connect thewood object and the cup with rope. Slowly put small weights in the cap. Give the object an initial speed with tapping. Collectdate by weighting the cup.
(2)Repeat step1) with 2 and 3 weight (50g)
(3)Repeat step1)2) to test the static coefficients of friction .But,cannot tap the object. Slowly put small weights until the objectstarts to move and accelerate.
(4)Repeat step 3) with 2 and 3 weights(50g)(5)Organize the data and calculate it.Observations and Calculation:F (k ) on a Flat Surface
F (s )on a Flat Surface
Sample conclusion: U (s )>U (k )(when the weight of object is equal and on the same surfaces )Analysis:
U(k) on a Flat Surface
U(s) on a Flat Surface
Conclusion:
1. The coefficient of friction (both Kinetic and static) is determined by the surfaces of both objects are contacting.
2. U(s)max always bigger than U(k).(when the weight of object is equal)
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