Q: A sound source emits a power of $$2.0 \ \mathrm{W}. $$What is the intensity at a distance of $$4.0 \ \mathrm{m}$$ from the source?

$$I = 9.95 \times 10$$^{-3}$$ \ \mathrm{W/m}^2$$

Question 1

A 2.0 m long copper wire has a cross-sectional area of $$1.0 	imes 10$$^{-6}$$ \ \mathrm{m}^2$$ and a resistivity $$ho = 1.7 	imes 10$$^{-8}$$ \ \Omega \cdot \mathrm{m}. $$What is the resistance of the wire?

Accepted Answer

$$R = 0.034 \ \Omega$$

Question 2

A mass $$m$$ attached to a spring with spring constant $$k$$ oscillates with amplitude $$A. At $$what position $$x is $$the kinetic energy equal to the potential energy?

Accepted Answer

$$x = \frac{A}{\sqrt{2}}$$

Question 3

Three resistors, $$R_1 = 2$$\ \Omega$$, R_2$ = 3\ \Omega$$, and $$R_3 = 6$$\ \Omega$$, are connected in parallel. What is the equivalent resistance R$$_{eq}$$?

Accepted Answer

$$R_{eq} = 1 \ \Omega$$

Question 4

A sound source emits a power of $$2.0 \ \mathrm{W}. $$What is the intensity at a distance of $$4.0 \ \mathrm{m}$$ from the source?

Accepted Answer

$$I = 9.95 	imes 10$$^{-3}$$ \ \mathrm{W/m}^2$$

Question 5

A mass of $$0.5\ \mathrm{kg} is $$attached to a spring with $$k = 200\ \mathrm{N/m}. $$What is the period of oscillation?

Accepted Answer

$$T = 0.314\ \mathrm{s}$$

Question 6

A string of length $$2.0\ \mathrm{m}$$ and mass $$0.01\ \mathrm{kg} is $$under a tension of $$50\ \mathrm{N}. $$What is the speed of a wave on the string?

Accepted Answer

$$v = 100\ \mathrm{m/s}$$

Question 7

A 12 V battery is connected to a $$4\ \Omega$$ resistor. What is the power dissipated by the resistor?

Accepted Answer

$$P = 36\ \mathrm{W}$$

Question 8

A sound has an intensity of $$1.0 	imes 10$$^{-6}$$\ \mathrm{W/m}^2. $$What is its sound level in decibels ($$\beta$$)?

Accepted Answer

$$\beta = 60\ \mathrm{dB}$$

Question 9

A diatomic gas is compressed adiabatically. What is the value of $$\gamma to $$use in calculations?

Accepted Answer

$$\gamma = 1.4$$

Question 10

A mass on a spring oscillates with $$x(t) = 0.10 \cos(2\pi 	imes 5 t). $$What is the maximum speed of the mass?

Accepted Answer

$$v_{max} = 3.14\ \mathrm{m/s}$$

Question 11

A $$10\ \Omega$$ and a $$20\ \Omega$$ resistor are connected in series to a $$30\ \mathrm{V}$$ battery. What is the current through the $$10\ \Omega$$ resistor?

Accepted Answer

$$I = 1.0\ \mathrm{A}$$

Question 12

A wire carries a current of $$2.0\ \mathrm{A}$$ for $$3.0\ \mathrm{s}. $$How much charge passes through the wire?

Accepted Answer

$$Q = 6.0\ \mathrm{C}$$

Question 13

A sound source moves away from you, doubling its distance. By what factor does the intensity decrease?

Accepted Answer

The intensity decreases by a factor of 4.

Question 14

A $$0.2\ \mathrm{kg}$$ mass oscillates on a spring with $$k = 50\ \mathrm{N/m}. $$What is the angular frequency $$\omega$$?

Accepted Answer

$$\omega = 15.8\ \mathrm{rad/s}$$

Question 15

A $$100\ \Omega$$ resistor is connected to a $$10\ \mathrm{V}$$ battery. How much energy is dissipated in 5 seconds?

Accepted Answer

$$E = 5.0\ \mathrm{J}$$

Question 16

A string has a linear density $$\mu = 0.005\ \mathrm{kg/m}$$ and is under a tension of $$20\ \mathrm{N}. $$What is the speed of a wave on the string?

Accepted Answer

$$v = 63.2\ \mathrm{m/s}$$

Question 17

A $$5.0\ \Omega$$ and a $$15\ \Omega$$ resistor are connected in parallel. What is the equivalent resistance?

Accepted Answer

$$R_{eq} = 3.75\ \Omega$$

Question 18

A sound wave has a frequency of $$440\ \mathrm{Hz}$$ and a wavelength of $$0.78\ \mathrm{m}. $$What is the speed of sound?

Accepted Answer

$$v = 343\ \mathrm{m/s}$$

Question 19

A mass on a spring has $$A = 0.20\ \mathrm{m}$$, $$k = 100\ \mathrm{N/m}$$, and $$m = 2.0\ \mathrm{kg}. $$What is the total mechanical energy of the system?

Accepted Answer

$$E = 2.0\ \mathrm{J}$$

Question 20

A $$9.0\ \Omega$$ and a $$6.0\ \Omega$$ resistor are connected in series. What is the equivalent resistance?

Accepted Answer

$$R_{eq} = 15.0\ \Omega$$

Electric Circuits and Oscillations: Key Equations and Concepts

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