Semester:Sept. 2015 – Jan 2016
Course:PHY440 Mechanics, Waves and Thermal Physics
Text book: Jewett, J.W. and Serway, R.A. (2010). Physics for Scientists and Engineers with Modern Physics, 8th Edition, Brooks/Cole Cengage Learning.
Assignment 3
Question / Topic / Problem1 / Section 10.1 Angular Position, Velocity, and Acceleration / No 4 (Softcopy) p.308; No 4 (Hardcopy) p. 308
4. A bar on a hinge starts from rest and rotates with an angular
acceleration = 10 + 6t, where is in rad/s2 and t is in seconds. Determine the angle in radians through which the bar turns in the first 4.00 s.
2 / Section 10.2 Analysis Model: Rigid Object Under Constant Angular Acceleration / No 8 (Softcopy) p.308; No 6 (Hardcopy) p. 308
8. A machine part rotates at an angular speed of 0.060 rad/s; its speed is then increased to 2.2 rad/s at an angular acceleration of 0.70 rad/s2. (a) Find the angle through which the part rotates before reaching this final speed. (b) If both the initial and final angular speeds are doubled and the angular acceleration remains the same,
by what factor is the angular displacement changed? Why?
3 / Section 10.6 Torque / No 36 (Softcopy) p.311; No 36 (Hardcopy) p. 311
36. The fishing pole in Figure P10.36 makes an angle of 20.0°
with the horizontal. What is the torque exerted by the fish about an axis perpendicular to the page and passing through the angler’s hand if the fish pulls on the fishing line with a force = 100 N at an angle 37.0° below the horizontal? The force is applied at a point 2.00 m from the angler’s hands.
4 / Conceptual Question / No 5 (Softcopy) p.338; No 9 (Hardcopy) p. 338
5. Both torque and work are products of force and displacement.
How are they different? Do they have the same units?
5 / Section 11.1 The Vector Product and Torque / No 5 (Softcopy) p.339; No 5 (Hardcopy) p. 339
5. Calculate the net torque (magnitude and direction) on the
beam in Figure P11.5 about (a) an axis through O perpendicular
to the page and (b) an axis through C perpendicular
to the page.
6 / Section 11.4 Analysis Model: Isolated System
(Angular Momentum) / No 41 (Softcopy) p.343; No 41 (Hardcopy) p. 343
41. A 0.005 00-kg bullet traveling horizontally with speed1.00 103m/s strikes an 18.0-kg door, imbedding itself10.0 cm from the side opposite the hinges as shown inFigure P11.41. The 1.00-m wide door is free to swing on its frictionless hinges. (a) Before it hits the door, does thebullet have angular momentum relative to the door’s axisof rotation? (b) If so, evaluate this angular momentum.
If not, explain why there is no angular momentum. (c) Isthe mechanical energy of the bullet–door system constantduring this collision? Answer without doing a calculation.(d) At what angular speed does the door swing open immediatelyafter the collision? (e) Calculate the total energyof the bullet–door system and determine whether it is lessthan or equal to the kinetic energy of the bullet before thecollision.
7 / Additional Problems / No 49 (Softcopy) p.370; No 49 (Hardcopy) p. 370
49. A 10 000-N shark is supported by a rope attached to a 4.00-m
rod that can pivot at the base. (a) Calculate the tension in the cable between the rod and the wall, assuming the cable is holding the system in the position shown in Figure P12.49. Find (b) the horizontal force and (c) the vertical force exerted on the base of the rod. Ignore the weight of the rod.
8 / Section 12.4 Elastic Properties of Solids / No 34 (Softcopy) p.368; No 36 (Hardcopy) p. 368
34. Review. A 30.0-kg hammer, moving with speed 20.0 m/s,
strikes a steel spike 2.30 cm in diameter. The hammerrebounds with speed 10.0 m/s after 0.110 s. What is theaverage strain in the spike during the impact?
9 / Additional Problems / No 63 (Softcopy) p.373; No 61 (Hardcopy) p. 372
63. A steel cable 3.00 cm2in cross-sectional area has a mass of
2.40 kg per meter of length. If 500 m of the cable is hung over a vertical cliff, how much does the cable stretch under its own weight? Take Ysteel= 2.00 1011N/m2.
10 / Section 15.2 Analysis Model: Particle in Simple Harmonic Motion / No 9 (Softcopy) p.458; No 9 (Hardcopy) p. 458
9. A 7.00-kg object is hung from the bottom end of a vertical
spring fastened to an overhead beam. The object is set into vertical oscillations having a period of 2.60 s. Find the force constant of the spring.
11 / Section 15.3 Energy of the Simple Harmonic Oscillator / No 21 (Softcopy) p.458; No 19 (Hardcopy) p. 458
21. A simple harmonic oscillator of amplitude A has a total energy E. Determine (a) the kinetic energy and (b) the potential energy when the position is one-third the amplitude. (c) For what values of the position does the kinetic energy equal one-half the potential energy? (d) Are there any values of the position where the kinetic energy is greater than the maximum potential energy? Explain.
12 / Additional Problems / No 52 (Softcopy) p.461; No 52 (Hardcopy) p. 461
52. An object attached to a spring vibrates with simple harmonic motion as described by Figure P15.52. For this motion, find (a) the
amplitude, (b) the period, (c) the angular frequency, (d) the maximum speed, (e) the maximum acceleration, and (f) an equation for its position x as a function of time.
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