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Unformatted text preview: 1. A 30kg child is swinging on a swing whose seat is a distance of 5.0m from the pivot point. Estimate the optimal time between pumps that the child should execute to increase her swinging amplitude. How does this time change for a 15.0 kg child? (11 got this right, 3 made a slight error, 13 didnt answer and 12 didnt know what to do). My best guess is to use the equation T= 2(pi)*square root of (I/mgL). However, we dont have the rotational inertia of the pendulum (I). However, it is apparent that if you change the mass, it will affect the time between pumps. use equation T=2piesqrootI/mgh so I=mLsqrd and the optimal time T=4.48sec so the finally answer for a 15kg child changes to T=4.49s i was not for sure how to plug in this data especially for I (for someone who did not know what to, this is VERY GOOD!) T = 2*pi*(L/g)^(1/2) The time does not change. The estimate time is 4.5 s. Physical Pendulum I = mghsin( ) but if <<1 then: = (mgh/I) Be careful to distinguish the physical angle from the phase angle here! Chapter 15 Problems...
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This note was uploaded on 01/21/2012 for the course ECE 476 taught by Professor Overbye,t during the Fall '08 term at University of Illinois, Urbana Champaign.
 Fall '08
 Overbye,T

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