Work & Energy, Circular Motion

Work & Energy, Circular Motion - Work & Energy,...

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Purpose: To apply the Work-Energy Theorem to a real-life problem. To investigate the forces and accelerations associate with circular motion. Apparatus: Hot Wheels car, Hot Wheels track, Hot Wheels car launcher, masking tape, timer, meter stick, Flying Cow hanging from string, spring scale (blue). Introduction The first activity of this lab is a complex problem that is to broken up into two main parts - Work & Energy and Circular motion. You will determine the energy stored in a Hot Wheels launcher and use that value to predict the minimum launcher setting that will enable the Hot Wheels to execute the loop-the-loop successfully on the first try . The second activity involves investigating the acceleration and forces on a Flying Cow going around in a circle. Theory The Work-Energy Theorem States that
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(in words) The net work done on an object equals its change in kinetic energy. (in Mathematics) W = KE f − KE i (1) Recall that the kinetic energy of an object is KE = 1 2 mv 2 The work done on an object is given by W = Fcos  s where s is the distance over which the force acts and the angle between the force and the displacement. For a single mass dropping to the floor from height h, the only force doing work (causing motion) is the gravitational force on the small mass, mg, which acts over the distance h, the height from which it drops to the floor. We can now expand on equation (1): mgh = 1 2 mv f 2 1 2 mv i 2 (2) The quantity mgh is the potential energy the mass acquires as it is moved from the floor (zero potential) to its starting point (mgh potential). (Incidentally, we could also have assigned zero as the potential energy before the fall and -mgh the potential on the floor) You can therefore read equation (2) as “the potential energy of a falling small mass is converted to its kinetic energy”. Note that you can also read the equation backwards , as in “a small mass thrown in the air has its kinetic energy converted to potential energy”.
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This note was uploaded on 06/22/2009 for the course PHYS 1101 taught by Professor Richardson, b during the Fall '08 term at Cornell University (Engineering School).

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Work & Energy, Circular Motion - Work & Energy,...

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