Physics 7A Fall 2006 Practice Problems
12/5/06
1
7A Final Review Questions
Note
: these are problems from previous quarters and are only meant to be a partial review of
problem types seen in Physics 7A. To prepare for the final exam you need to study a) the DL
activities and know the meaning/purpose of each one—identify the models being used and why, b)
the FNTs and what each problem was teaching you in terms of the models, c) your quizzes and the
mistakes you made and whyhow can you not make that mistake again? Did you not give a
complete justification of your answerwatch for this as it is the leading cause for not getting much
credit, and d) your lecture notes.
When doing the problems
below
ask yourself what model you
are using and why. That way you will recognize which model to use on the exam instead of
memorizing any particular solution and trying to recall a solution! Always explain/justify your
answers. Don’t assume anything is too obvious or trivial to mention; the grader wants to know you
really understand.
1)
Olaf the Snowboarder (70 kg, including his snowboard) is on the top of an inclined slope at an
initial height of 50 m
.
Olaf snowboards down the slope; then Olaf moves 10 m over bumpy
snow that imparts a frictional force of 600 N against his direction of motion; then Olaf finally
compresses a
k
= 8000 N/m spring by a maximum displacement
x.
The only friction he
encounters is over the bumpy snow. The drawing below is not to scale. Hint: Olaf does work
going through the bumpy snow.
50m
O
l
a
f
bumpy snow
10m
²
x
uncompressed spring
(a)
Draw a properly labeled energy interaction diagram for Olaf during this entire process.
(b)
Find the maximum displacement
x
of the spring for the case of Olaf having
no
initial
velocity. [x = 2.66 m]
2)
The molar heat capacity of a certain ideal gas is measured (for a constant volume process) to
be 3
R
= 24.94 J/mol·K at a temperature of 27° C.
(a)
Find the thermal energy of 3.5 moles of this gas. [Eth = 26,187 J]
(b)
The gas is cooled from its initial temperature to –17° C. During this process 965 J of
energy is transferred out of the gas system as heat. Calculate the work done. Specify
whether the work is done on or by the system. [W = –2,876 J]
Δ
x
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View Full DocumentPhysics 7A Fall 2006 Practice Problems
12/5/06
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3)
Thjodhild drops a 0.15 kg iceball off a cliff, into the sea 200 m below.
Both the iceball and the sea are at 0° C. Assume that when the iceball
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 Summer '08
 PARDINI
 Physics, Thermodynamics, Energy, Entropy, Heat, energy interaction diagram

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