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lab report 2 practical
Energy and Motion (PHY10001)
Swinburne University of Technology
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Laboratory 02: Coefficient of static friction and coefficient of kinetic friction (μs & μk) Ɵ Darsha Dulanjalee Gunawardena Student no: 102001403 Date: 05th November, 2018 Partners: Dinith, Udam, Pasidu Mg Three different types of blocks with different mass and area made from different materials (wood and metal) are used in this experiment whether to determine they affect the change of coefficient of frictions. Newton’s second law is applied to the object on the inclined ramp for both instances. Determining coefficient of static friction When the object is in a static position, with no movement, the acceleration of the system is zero. The object is in equilibrium. Applying F = ma in the horizontal direction parallel to the plane, Mg SinƟ – FFric = M(0) Mg SinƟ = FFric Applying F = ma in the vertical direction perpendicular to the plane, N – Mg CosƟ = M(0) FFric = μs N Mg CosƟ = N μs = Mg SinƟ/Mg CosƟ μs = TanƟ Determining the coefficient of kinetic friction When the object is moving (sliding down the ramp) there is a constant acceleration in the system down the plane. Applying F = ma in the vertical direction perpendicular to the plane, N – Mg CosƟ = M(0) FFric = μk N Mg CosƟ = N μk = Mg SinƟ/Mg CosƟ μk = TanƟ Applying F = ma in the horizontal direction parallel to the plane, Mg SinƟ – FFric = Ma Mg SinƟ – μk Mg CosƟ = Ma μk = To determine the acceleration of the object, the time taken (t) for the object to travel x distance is calculated. The object starts from rest, therefore initial velocity is zero. Therefore, Method Three different blocks with masses M, 2M, 2M and surface areas, A, A, 2A respectively are used in this experiment. They are tested individually. Testing for the coefficient of static friction, First, one block is placed on a ramp and the ramp is slowly inclined so that the block begin to slip down the ramp. The height of the ramp from the base and the horizontal length for the initial position of the block is measured. This procedure is repeated for three more times and for each block individually. Afterwards, the coefficient of static friction can be found by dividing the height by the horizontal length as it gives TanƟ which is equivalent to the coefficient of static friction. Testing for the coefficient of kinetic friction, The block is placed on its initial position and the ramp is inclined slowly till the block slip all the way down the ramp up to the final marked position on the ramp. The time is calculated by the block to travel this distance by a stopwatch, and three readings are taken for accuracy. This is carried on thrice for all three blocks individually. The distance travelled by these three blocks are constant and same for all three. The experiment is conducted in this manner to get an accurate value for the coefficient of friction. If it was conducted by sliding it across a horizontal plane without an inclination, it will require an external force provided by the experimenter and it would be exceptionally harder to carry on the experiment with accurate values. Instead of the horizontal force downward being equal to the divided component of mg, there will be a force acting on the object provided by the experimenter and it will be unknown. It will be more time consuming and complicated to use this method. Using an inclined plane, the block slips without any external forces provided by another object. Therefore it is more accurate and simple. For coefficient of kinetic friction Trial 01 Block Xd T (cm) (s) Trial 02 Ɵ H X Xd T (cm) (S) Ɵ Trial 03 Ɵ Xd (cm) H X (⁰) T Ɵ (s) Ɵ H X (⁰) Ɵ (⁰) (M,A) 41 0 23 54 23 41 1 23 53 23 41 0 23 54 23 (2M,A) 41 1 22 49 24 41 1 22 49 24 41 1 22 49 24 (2M,2A) 41 1 21 49 23 41 1 21 50 22 41 1 21 50 22 Calculations; For [M,A]; <T> = = 0 = 23⁰ <Ɵ> = = μk = =0 ms-1 = = 0 For [2M,A]; <T> = = 1 = 24⁰ <Ɵ> = = μk = =0 ms-1 = 0 = For [2M,2A]; <T> = = 1 = 23⁰ <Ɵ> = = μk = =0 ms-1 = = 0 For [2M,2A] σ= √∑ σ= √ √ √ = 0 μs = 0 ± 0 Coefficient of kinetic friction For [M,A] σ= √∑ σ= √ √ √ = 0 μk = 0 ± 0 For [2M,A] σ= √∑ σ= √ √ μk = 0 ± 0 √ = 0 For [2M,2A] σ= √∑ σ= √ √ √ = 0 μk = 0 ± 0 Conclusion Based on the experimental values, the prediction that coefficient of static friction is greater than the coefficient of kinetic friction was proved to be true. The mass does not have a direct effect on the coefficient of frictions but when the weight of an object increase, the mass increases. Hence, the inclination of the ramp, or the inclination between the two planes decrease. Depending on the mass the inclination either increases or decreases. Moreover, the surface area does not have any effect on the coefficient of frictions either. Using materials with a high coefficient of friction helps to minimize errors because higher the coefficient, lessen the chance to detect errors. Comparing the calculated values of μk and μs, at all three instances it satisfied the predications that μs > μk . Group 01 For [M,A] μs = 0 μk= 0 For [2M,A] For [2M,2A] μs = 0 μk= 0 μs = 0 μk= 0
lab report 2 practical
Course: Energy and Motion (PHY10001)
University: Swinburne University of Technology
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