In the figure here three ballot boxes are connected by cords, one of which wraps
ID: 2137720 • Letter: I
Question
In the figure here three ballot boxes are connected by cords, one of which wraps over a pulley having negligible friction on its axle and negligible mass. The masses are mA = 25 kg, mB = 44 kg, and mC = 12 kg. When the assembly is released from rest, (a) what is the tension in the cord connecting B and C, and (b) how far does A move in the first 0.200 s (assuming it does not reach the pulley)?
Explanation / Answer
For motion of box A,
T1 =25a...................(1)
For motion of box B,
44g + T2 -T1 =44a....(2)
For motion of box C,
12g - T2 = 12a..........(3)
Adding equations(1),(2) and (3)
56g =81a
a =56*9.8 / 81
a = 6.775 m/s^2
From equation (3)
T2 = 12 (g -a )
T2 = 12(9.8 - 6.775)
T2 = 36.3 N
(a)The tension in the cord that connects boxes B and C is 36.3 N
For b).
box A move in the first 0.200 s a distance =s = (1/2)at^2
s = 0.5*6.775*(0.200)^2=0.1355 m
(b)Box A moves 0.1355 m in the first 0.200 s
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