physics 117 mock midterm - answer key · phys 117 mock midterm exam answers 14 question b4 c),...

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

http://library.usask.ca/studentlearning

http://library.usask.ca/sss

Phys 117 Mock Midterm Exam Answers 2

Part A – Multiple Choice Questions

1. E

2. C

3. C

4. D

5. C


6. E

7. A

8. B


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

,


#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


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


Part B – Long Answer Questions

B1.

a)

b) Note that 𝑃𝐵 = 𝑃𝐴 + 𝜌𝑤𝑔ℎ where 𝜌𝑤 = density of water

Bernoulli’s principle:


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)


B2.

a)

𝑥 = (5.00cm) cos ((35.3 rad/s)(0.0950s)) = −4.89 cm

b) Spring force:


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)


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


b)

𝐴 =(0.817

ms

)(2.00 s)

2𝜋= 0.260 m


B4.

a)

b)

c)


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!

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physics 117 mock midterm - answer key · phys 117 mock midterm exam answers 14 question b4 c),...

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