Unformatted text preview: P7A Quiz4a DL Sec____ Name (last)______________________
I certify by my signature that I will abide by the code of academic conduct of the University of California. (first) ___________________ Rubric Codes: Signature________________________________________ Name: DL Sec. 7A Quiz 2 1. A 0.5 kg golf ball is thrown vertically downward with an initial speed of 7 m/s from 6 meters Last 6 digits of ID # Signature: above the ground by a person on a roof top. No books [or pts] What is the speed of the all your work below. Answers alone do ill inreceive credit! a. 8 notes. Calculators OK. Show ball right before it hits the ground? F not the blank and clearly show us how you got that answer 1) Two masses are connected by a string your is hung . You may assume the effects of friction and Ma energy transfer mass Mb falls it pulls mass over a massless pulley. As to thermal systems are negligible. The the top of the table. At the instant Ma to the right alongspeed of the ball right before it hits the ground (in m/s): ____________ when the masses are in the positions shown in the Mb diagram they are already in motion, and moving at a velocity vi = 1 meter/sec. After mass Mb falls through an additional 3 meters both masses will be moving at a velocity of vf = 2 meter/sec. (Ma = 4 kg, Mb = 3 kg) 3m a) Is any energy being converted to thermal energy as the masses increase their velocity from 1.0 m/s to 2.0 m/s? You must fully justify your answer. Correct answers with no explanation will receive reduced credit. You may find an energy diagram useful in your explanation. b. [12 pts] Plot the PEgrav, Etotal, and KE of the ball on the graph below as functions of height (y) by defining y=0 at 3 meters above the ground. Plot the energies over the y values that the ball occupies during this process and clearly label each energy. Be sure that the plotted initial and final values of each energy are correct. b) In the graph to the right sketch (and label) reasonable graphs of the following energies as functions of the height (yb) of Mb as this mass drops these 3 m. Show your chosen initial height and the final height on the horizontal axis. i) PEgrav of Mb ii) PEgrav of Ma iii) KE of Ma iv) Etotal of the entire system (including all thermal energy systems) Useful equations and constants PEspring = ! k( x)2
Physics 7A Quiz 2 Summer I 2009 Energy (J) Height (yb) KE = ! mv2 PEgrav = mgy g = 10 J/kg m Eth = mc T Ebond = m H
1 Useful equations/constants: g = 10 m/s2 PE = mgy KE = (1/2)mv2 ...
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- Winter '08
- Mass, energy systems, transfer mass Mb, DL Sec. 7A, P7A Quiz4a DL