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Student Learning Services (SLS) is a unit of the University Library that offers many kinds of
learning support to students, including Structured Study Sessions. You can find more information
about SLS online at http://library.usask.ca/studentlearning .
Physics 117 Mock Midterm - Answer Key Sunday, February 10th, 2019 * 2pm * Arts 241
Note: This mock test consists of questions covered in Physics 117. This test is not
comprehensive. The problems on this test were compiled by your SSS peer mentors, and
not your professors, and are based on problems from old exams, found on the website
http://physics.usask.ca/~bzulkosk/phys117/index.html . (Note: The figures and diagrams
have also been taken from old tests.) **This mock test should not be viewed as a
‘preview’ of the actual test, and you should not rely solely on it for your test
preparation.**
Students should also be aware that the real midterm exam will consist of 12 multiple
choice questions and 4 long-answer questions in a ‘scratch card’ format. The mock
midterm has 15 multiple choice questions and 4 long-answer questions in a ‘show your
work’ format.
If you think you’ve found an error, please email the Phys 117 SSS team at [email protected] .
Thank you!
Answers to Multiple Choice questions
1 E 4 D 7 A 10 E 13 D
2 C 5 C 8 B 11 B 14 B
3 C 6 E 9 none 12 A 15 A
Answers to Long-Answer questions
B1. a) 𝑣𝐴 = 4𝜐 b) 𝜐 = 4.21 m/s c) 0.0331 m3/s or 3.31 × 10−2 m3/s
B2. a) 𝑥 = −4.89 cm b) magnitude of the force = 22.9 N c) 𝜐 = 0.371 m/s or 37.1 cm/s.
B3. a) 0.817 m/s b) 0.260 m
B4. a) 𝑓𝑛 = 𝑛 (𝜐
2𝐿) b) 4.00 Hz c) 129 m
Detailed solutions follow.
Phys 117 Structured Study Session Information
Mondays 4:00-5:20pm - Room G3 in the Murray Library (Rey)
Tuesdays 4:30-5:50pm – Room 213 in the Arts Building (Yen)
Wednesdays 2:30-3:50pm – Room 102 in the Arts Building (Michael)
Website: http://library.usask.ca/sss
Phys 117 Mock Midterm Exam Answers 4
9. None of the answer choices is correct
10. E
So the difference in decibel level 𝛽2 − 𝛽1 is:
Since log (1
3) is negative, the difference in decibel level is negative, so the decibel level
decreases. And since log (1
3) ≅ −0.477,
𝛽2 − 𝛽1 ≅ 10 dB (−0.477) ≅ −4.77 dB So the decibel level goes down by less than 10 dB. So answer E is correct.
11. B
,
Phys 117 Mock Midterm Exam Answers 5
#11, continued
The distance is 1 km = 1000 m, so the time at 0℃ is: 𝑡0 =distance
velocity=
1000 m
331 m/s= 3.02 s.
The time at -35℃ is 𝑡−35 =distance
velocity=
1000 m
309 m/s= 3.24 s .
The noise travels more slowly on the cold day, by approximately 0.22 s .
12. A
𝐼 ∝ 1
𝑟2
so if 𝑟 decreases, then 𝐼 increases.
13. D
14. B
Phys 117 Mock Midterm Exam Answers 6
15. A
Rewriting 𝑓2 gives:
𝑓2 = √𝐹1
𝜇1√4
1
4𝐿1= √
𝐹1
𝜇1
1
2𝐿1
This is the same as 𝑓1 (boxed expression above), so the answer is A.
End of Part A
Phys 117 Mock Midterm Exam Answers 7
Part B – Long Answer Questions
B1.
a)
b) Note that 𝑃𝐵 = 𝑃𝐴 + 𝜌𝑤𝑔ℎ where 𝜌𝑤 = density of water
Bernoulli’s principle:
Phys 117 Mock Midterm Exam Answers 8
Question B1 b), continued
Since 𝑃𝐵 = 𝑃𝐴 + 𝜌𝑤𝑔ℎ, we get:
𝑃𝐴 +1
2𝜌(16𝜐2) = 𝑃𝐴 + 𝜌𝑤𝑔ℎ +
1
2𝜌 𝜐2
1
2𝜌(16𝜐2) −
1
2𝜌(𝜐2) = 𝜌𝑤𝑔ℎ
1
2𝜌(15𝜐2) = 𝜌𝑤𝑔ℎ
15
2𝜌𝜐2 = 𝜌𝑤𝑔ℎ
𝜐2 =2𝜌𝑤𝑔ℎ
15𝜌
𝜐 = √2𝜌𝑤𝑔ℎ
15𝜌= √
2 (1.00 × 103 kgm3) (9.80
ms2) (0.0175 m)
15 (1.29kgm3)
𝜐 = 4.21 m/s
c)
Phys 117 Mock Midterm Exam Answers 9
B2.
a)
𝑥 = (5.00cm) cos ((35.3 rad/s)(0.0950s)) = −4.89 cm
b) Spring force:
Phys 117 Mock Midterm Exam Answers 10
Question B2 b), continued
So 𝑘 = 𝜔2𝑚. Substituting 𝜔 = 35.3 rad/s and 𝑚 = 0.375 kg gives
𝑘 = (35.3 rad/s)2(0.375 kg) = 467 kg/s2
So the force is
c)
Phys 117 Mock Midterm Exam Answers 11
B3.
a)
Simplifying:
Since 𝑓𝑜𝑚𝑎𝑥− 𝑓𝑜𝑚𝑖𝑛
= 2.10 Hz,
2.10 = 2𝑓𝑠
𝜐0
𝜐
Solving for 𝜐0 gives:
𝜐0 =𝜐(2.10 Hz)
2𝑓𝑠=
(343ms ) (2.10 Hz)
2(441 Hz)= 0.817 m/s
Phys 117 Mock Midterm Exam Answers 14
Question B4 c), continued
Since 𝑛 must be an integer, we take 𝑛 = 3.
Solving 𝑓𝑛 = 𝑛𝜐
2𝐿 for 𝐿 and then using 𝑛 = 3:
𝐿 =𝑛𝜐
2𝑓𝑛=
3 (344ms )
2(4.00 Hz)= 129 m
End of Part B -- Good luck with your exams!
Do you want to help other students? Apply to be a PAL Peer Mentor for Fall 2019!
We are recruiting volunteers for the Peer Assisted Learning (PAL) program for the
2019/2020 academic year. Develop your leadership, mentorship and presentation skills
while assisting other students to be successful. We are seeking students who are:
- interested in sharing their own academic experiences in an interactive and
informal setting;
- upper year students with a 75% average or higher; and who are available 5 or 10
hours/week depending on the volunteer role/PAL program
The deadline to apply is Tuesday, February 26, 2019.
Do you have a question or want more information?
Visit library.usask.ca/pal to learn more or apply. Feel free also to send email to