10 Physics Questions

1. [5 points] When a 2-kg mass oscillates on a spring at the frequency of 10 Hz. What will the frequency be if 0.5 kg are (a) added to the original mass and (b) subtracted from the original mass?

2. [10 points] A block of mass 0.5 kg is attached to a spring and is moving in simple harmonic motion on a frictionless horizontal surface. The amplitude of the motion is 0.25 m and the period is 2.0 s. When the block is at x = 0.1 m, what are

(a) the speed, (b) the acceleration, (c) the potential energy and (d) the kinetic energy

of the block? And what are (e) the total energy, (f) the maximum speed and (g) the maximum acceleration of the block?

3. [10 points] (a) Write the expression for y(x,t) for a sinusoidal wave traveling along a rope in the negative x

direction with amplitude = 5 cm, wavelength =10 cm and frequency = 4 Hz. Given that y(0,0)= 0 . (b) From part (a), write the expression for the transverse velocity and acceleration of the rope as a function of position x and time t.

4. [5 points] A 1.2-m string of mass 12 g is tied to the ceiling at its upper end, and the lower end supports a mass M. Neglect the very small variation in tension along the length of the string that is produced by the

weight of the string. When you pluck the string slightly, the waves traveling up the string obey the equation

y(x,t)=(2 mm)cos�(9.8 m−1)x−(490 s−1)t� �� Assume that the tension of the string is constant and the gravitational acceleration = 9.8 m/s2 . (a) What is the wavelength of the wave? (b) How much time does it take a pulse to travel the full length of the string? (c) Determine the value of the mass M?

5. [5 points] A point source emits 30.0 W of sound. At 100 m from the source, a small microphone 2

intercepts the sound in an area of 0.5 cm . Calculate (a) the sound intensity and (b) the intensity level at the location of the microphone (c) What is the power intercepted by the microphone?

6. [5 points] In the figure, sound with a 40.0 cm wavelength travels rightward from a source and through a tube that consists of a straight portion and a half-circle. Part of the sound wave travels through the half- circle and then rejoins the rest of the wave (this rejoining results in interference). What is the smallest radius r that results in an (a) intensity maximum and (b) intensity minimum at the detector?

7. [5 points] In the figure, S is a speaker driven by an variable oscillator with a frequency that can be varied from 800 Hz to 2500 Hz, and D is a cylindrical pipe with two open ends and a length of 50 cm.

(a) What is the fundamental frequency of this pipe? (b) What are the (b) lowest and (c) highest frequencies at which

resonance occurs? [Take the speed of sound in the pipe to be 350 m/s.]

8. [5 points] A siren emitting a sound of frequency 1200 Hz moves away from you toward the face of a building at a speed of 10 m/s. Take the speed of sound in air as 340 m/s. (a) What is the frequency of the sound you hear coming directly from the siren? (b) What is the frequency of the sound you hear reflected off the building?

9. [5 points] Light is incident normally on the left face of a prism as shown in the figure. A liquid layer is placed on the top face of the prism. If the index of refraction of the prism is 1.5, what is the maximum index that the liquid may have if the light is to be totally reflected from the top face.

10. [5 points] An object is 25 cm to the left of a diverging len. A converging lens (focal length = 12 cm) to the right of the diverging lens as shown in the figure. The final image from this lens system is at 17 cm to the right of the converging lens.

(a) What is the focal length of the diverging lens? (b) If the object is 10 cm tall. What is the height of the image? (c) Is the final image upright or inverted?