I have been working through my physics study guide for a couple of hours now and

Question

I have been working through my physics study guide for a couple of hours now and I am just stuck on a few problems:

1. A barking dog delivers about 1.0mW of power, which is assumed to be uniformly distributed in all directions. What is the intensity level in decibels at a distance 5.00 m from the dog? The threshold of human hearing is 1.0 X 10^-12 W/m^2.

a. 61 dB

b. 63 db

c. 65 dB

d. 68 dB

2. When a guitar is tuned to adjust pitch, what is it what is changed?

a. The wavelength of the fundamental

b. The frequency of the fundamental

c. The amplitude of the fundamental

3. Two small objects, with masses m and M, are originally a dstance r apart, and the magnitude of the gravitational force on each one is F. The masses are changed to 2m and 2M, and the distance is changed to 4r. What is the magnitude of the new gravitational force?

a. F/16

b. F/4

c. 16F

d. 4F

e. F/2

4. A mass on a spring undergoes SHM. When the mass is at its maximum distance from the equillibrium position, which of the following statements about it are true? (There can be more than one correct choice).

a. Its acceleration is zero

b. Its speed is zero

c. Its elastic potential energy is zero (the potential energy would be at max - so c isn't correct)

d. Its kinetic energy is a maximum (Its kinetic energy would be at zero - so d isn't correct).

e. Its total mechanical energy is zero

5. An object attached to an ideal spring oscillates with an angular frequency of 2.81 rad/s. The object has a maximum displacement at t=0.00s of 0.232m. If the force constant (spring constant) is 29.8 N/m, what is the potential energy stored in the mass-spring system when t=1.42s?

a. 0.350 J

b. 0.256 J

c. 0.329 J

d. 0.399 J

Any help on any of these would be much appreciated. If you could just explain how you got your answer as well....I rate quickly.

Thanks :)

Explanation / Answer

My answers are:

1A

2B

3B

4D

5C

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