mbrmbrg
Oct22-06, 01:11 PM
Three boxes (A, B, and C) are connected by cords, one of which wraps over a pulley having negligible friction on its axle and negligible mass. Box A is on a frictionless table, boxes B and C hang over the side of the table.
The masses are mA = 30.0 kg, mB = 40.0 kg, mC = 18.0 kg.
(a) When the assembly is released from rest, what is the tension in the cord that connects boxes B and C?
60.1 N
(b) How far does box A move in the first 0.250 s (assuming it does not reach the pulley)?
0.202 m
Answers given are the book's answer's. (Actually, part b used to be my answer also, but I can't duplicate it...)
I'd like to start by calculating tension in the string connecting A to B&C, and then say that for A in the x direction, \Sigma\ F=T=m_Aa, and then use a to find delta x. Unfortunately, since the system is in motion, T\neq\ (m_B+m_C)g, and I don't know how to find it.
The masses are mA = 30.0 kg, mB = 40.0 kg, mC = 18.0 kg.
(a) When the assembly is released from rest, what is the tension in the cord that connects boxes B and C?
60.1 N
(b) How far does box A move in the first 0.250 s (assuming it does not reach the pulley)?
0.202 m
Answers given are the book's answer's. (Actually, part b used to be my answer also, but I can't duplicate it...)
I'd like to start by calculating tension in the string connecting A to B&C, and then say that for A in the x direction, \Sigma\ F=T=m_Aa, and then use a to find delta x. Unfortunately, since the system is in motion, T\neq\ (m_B+m_C)g, and I don't know how to find it.