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Olin [163]
3 years ago
8

What is the change in internal energy if 20 J of heat is released from a system and the system does 50 J of work on the surround

ings?
a. -70 j
b. 30 j
c. -30 j
d. 70 j
Physics
2 answers:
viva [34]3 years ago
8 0

OPTION - A

Change in energy given by :-

dQ = du + dw

dQ = -20 - (-50)

dQ = -70

siniylev [52]3 years ago
7 0
Answer is A.

Both energy changes describe energy be lost from the system (in different forms - as heat or as work). The negative sign indicates loss.
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F_{1}=\frac{kq_{1} q }{d^2}\\F_{1}=\frac{(8.99*10^9)(25*10^{-6}C)(8.4*10^{-6}C)}{(0.18m)^2}=58.26 N\\

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F_{T}=F_{1} - F_{2}\\25N=58.26N-F_{2}\\F_{2}=58.26N-25N=33.26N\\\mid F_{2} \mid=\frac{kq_{2}q}{d^2}

Rewriting for q_{2}:

q_{2}=\frac{F_{2}d^2}{kq}\\q_{2}=\frac{33.26N(0.34m)^2}{8.99*10^9\frac{Nm^2}{C^2}(8.4*10^{-6}C)}=50.91*10^{-6}C=50.91 \mu C

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