EF 152 Exam #2, Spring 2016 Page 1 of 6

Size: px

Start display at page:

Download "EF 152 Exam #2, Spring 2016 Page 1 of 6"

Judith Dickerson
6 years ago
Views:

1 EF 152 Exam #2, Sprig 2016 Page 1 of 6 Name: Sectio: Istructios Sit i assiged seat; failure to sit i assiged seat results i a 0 for the exam. Do ot ope the exam util istructed to do so. Do ot leave if there is less tha 5 miutes to go i the exam. Whe time is called, immediately stop writig, remai seated, ad pass your exam to the ceter aisle. Do ot stad up or leave util all exams have bee collected. Workig after time is called results i a automatic 10 poit deductio. Guidelies Assume 3 sigificat figures for all give umbers uless otherwise stated Show all of your work o work, o credit Harmoic Motio ω agular frequecy A amplitude k stiffess m mass δ phase agle x 0 iitial displacemet v 0 iitial velocity T period f frequecy x(t) = A si(ωt + δ) = a 1 si(ωt) + a 2 cos(ωt) v(t) = Aω cos(ωt + δ) = a 1 ω cos(ωt) a 2 ω si(ωt) a(t) = Aω 2 si(ωt + δ) = a 1 ω 2 si(ωt) a 2 ω 2 cos(ωt) ω = k m A = a a 2 a 1 = v 0 a δ = ta 1 ( a ω 2 = x 0 2 ) a 1 T = 2π f = 1 ω = 2πf ω T Wave Equatio v wave velocity A amplitude k wave umber ω agular frequecy λ wavelegth f frequecy y(x, t) = A cos (kx ωt) v is positive if sig of ω is egative. v = λf k = 2π λ Parallel Axis Theorem I = I CM + mr 2 Pedulums simple: ω = g l physical: ω = mgr I Speed of Soud v = B B Bulk Modulus ρ ρ mass desity Speed of Soud i Air: v ( T)m/s (T i ) v (20.05 T)m/s (T i K) Natural frequecies λ wavelegth L Legth harmoic T tesio μ mass per uit legth f frequecy v wave velocity i medium Strig: λ = 2L f = v λ = 2L T μ Air Colums: λ = 4L λ = 2L closed ( = 1, 3, 5, ) ope ( = 1, 2, 3, ) Wave Speed: Cables, Ropes, etc. T Tesio μ mass per uit legth E Modulus of elasticity ρ mass desity Trasverse: v = T μ Logitudial: v = E ρ Soud Level β(i db) = 10 log I I 0 I Itesity I 0 referece itesity, W/m 2 Doppler Shift f 0 frequecy f shifted frequecy v velocity of soud i medium v L velocity of listeer v S velocity of source f = f 0 v+v L v+v S Beat Frequecy: f 1 f 2 I = + listeer to source Wave Eergy, Power, Itesity E eergy I itesity P power P average power E = 2π 2 μvtf 2 A 2 P = P = 2π 2 μvf 2 A 2 P = 4π 2 μvf 2 A 2 cos 2 (kx ωt) Light Waves Law of Reflectio: P I 2 4πr 2 = r 2 1 I 1 θ r = θ a Idex of refractio: = c v Sell s Law: r 2 2 a si θ a = b si θ b Light wavelegth: λ = λ 0 Total Iteral Reflectio: si θ crit = b a speed of light i vacuum: c = m/s

2 EF 152 Exam #2, Sprig 2016 Page 2 of 6 [This page itetioally left blak]

3 EF 152 Exam #2, Sprig 2016 Page 3 of 6 1. (2 pt) Determie the harmoic of this ope pipe: a. First b. Secod c. Third d. Fourth e. Fifth Based o the graph showig simple harmoic motio, aswer the followig questios: 2. (2 pt) What is the period of the system closest to? a. 0.4 sec b. 0.9 sec c. 1.2 sec d. 1.6 sec 3. (2 pt) What is the amplitude of the system? a m b m c m d m 4. (2 pt) Whe the positio is at a maximum, what is the acceleratio? a. Positive b. Zero c. Negative d. Caot tell from this graph 5. (6 pt) The speed of soud is 343 m/s i 20 o C air. If we measure the speed of soud to be 357 m/s, what is the temperature o that day? 6. (6 pts) Dr. Biegalski has a clock o her desk made of a ball hagig from a strig. If the strig is 0.36 m log, what is the period of the clock?

4 EF 152 Exam #2, Sprig 2016 Page 4 of 6 7. (10 pt) A mass (m = 2 kg) vibrates i simple harmoic motio o a sprig. The sprig has a stiffess of 40,000 N/m. If the maximum velocity of the system is 5.7 m/s, what is the amplitude of the motio? 8. (14 pt) A object of ukow shape (m = 3.1 kg) oscillates at 2 Hz at a distace of 4 cm from its ceter of mass. What is the ew frequecy if the same object is hug from a distace of 7 cm from its ceter of mass?

5 EF 152 Exam #2, Sprig 2016 Page 5 of 6 9. (14 pt) A computer speaker uses 1.5 W of power to geerate a desired soud level at 2 m away from the speaker. What is the speaker s soud level at 8 m away? 10. (14 pt) You are drivig east at 87 mph. A car with a sire is drivig west at 73 mph. As you approach the other car, you hear a frequecy of 477 Hz. If the sire is made of a ope pipe, what is the legth of the pipe? Assume v = 343 m/s (767 mph) ad the soud is the fudametal frequecy.

6 EF 152 Exam #2, Sprig 2016 Page 6 of (14 pt) A guitar has two strigs. Strig 1 (m 1 = 3 g) plays a frequecy of 397 Hz ad Strig 2 plays a frequecy of 522 Hz. If the strigs are made of the same material, have the same legth, ad have the same tesio, what is the mass of strig 2? 12. (14 pt) Light travels i a mystery material at a speed of 1.24 x 10 8 m/s ad at a frequecy of 6.2 x Hz. What is the refractio agle as the light eters the mystery material from the air at 11 o from the perpedicular?

EF 152 Exam 2 - Spring, 2017 Page 1 Copy 223

EF 152 Exam 2 - Spring, 2017 Page 1 Copy 223 Instructions Do not open the exam until instructed to do so. Do not leave if there is less than 5 minutes to go in the exam. When time is called, immediately