- #1
Cc518
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Homework Statement
Object A is stationary while objects B and C are in motion.
Forces from object A do 10 J of work on object B and –5 J of
work on object C. Forces from the environment do 4 J of work
on object B and 8 J of work on object C. Objects B and C do
not interact. What are ΔKtot and ΔU if (a) objects A, B, and C
are defined as separate systems and (b) one system is defined to
include
objects A, B, and C and their interactions?
Homework Equations
ΔEsys 2 = ΔKtot + ΔU = (WA + WB+WC) + ΔU = 0
The Attempt at a Solution
I get WB=14J and WC=3J. I just don't understand why WA is not -5J. Apparently C and B exert forces onto A, right? So ΔKtot = 14 + 13 -5 =12J, but the answer is 17J.
For part B, I thought ΔU = -ΔKtot= -12J, but the answer is -5J.
Any help is appreciated!