PHYS 218 Midterm: Texas A&M Physics 218 Exam2_Fall_2014Solutions
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Calculate (a) the net force acting on the bob, and the angle between the wire and the vertical, (b) what work should be done by friction in order to stop the pendulum. Answer to question (a): plugging eqs. (1) and (2) into eq. (3), one finds for the angle cos =(g/l)t2/ (2 )2 and for the net force f=tsin = mg tan . Answer to question (b) follows from the work-energy theorem w=-mv2/2 -mgl(1-cos ), where v2=(2 l/t)2 (1-cos2 ). cos =0. 025, =88. 600 , f= =(1570 30) n, w=-2070 j. Problem 4: a 500 g block is released from the top of a 45 incline. The block is initially at a distance of. D=80 cm from the free end of a long massless spring that lies on the incline"s surface with its other end held fixed at the bottom edge of the incline. The unstretched length of the spring is l= 17 cm.
