Q: A cylindrical container full of alcohol (density $$800\ \mathrm{kg/m^3$}) $$has a diameter of $$10\ \mathrm{m}$$ and a $$5\ \mathrm{m}$$ depth. What is the absolute pressure at the bottom of the container? (Assume atmospheric pressure is $$1.01 \times 10^5$\ \mathrm{Pa}.)$$

$$1.41 \times 10^5$\ \mathrm{Pa}$$

Q: The power of a train whistle is $$3\ \mathrm{W}$$ and the sound intensity at a distance of $$10\ \mathrm{m} is $$measured. What is the sound intensity?

$$2.4 \times 10$$^{-3}$$\ \mathrm{W/m^2$}$$

Q: The sound from a jackhammer has a sound intensity level of $$90\ \mathrm{dB} at a $$distance of $$30\ \mathrm{m}. $$What is the sound intensity?

$$1.0 \times 10$$^{-3}$$\ \mathrm{W/m^2$}$$

Question 1

A cylindrical container full of alcohol (density $$800\ \mathrm{kg/m^3$}) $$has a diameter of $$10\ \mathrm{m}$$ and a $$5\ \mathrm{m}$$ depth. What is the absolute pressure at the bottom of the container? (Assume atmospheric pressure is $$1.01 	imes 10^5$\ \mathrm{Pa}.)$$

Accepted Answer

$$1.41 	imes 10^5$\ \mathrm{Pa}$$

Question 2

Suppose you add $$10\ \mathrm{m^3$} of $$brine (density $$1100\ \mathrm{kg/m^3$}) to a $$large open cylindrical tank of radius $$10\ \mathrm{m}. $$What is the increase in depth of the brine?

Accepted Answer

$$0.032\ \mathrm{m}$$

Question 3

A rectangular block of wood with mass $$0.5\ \mathrm{kg}$$ and dimensions $$0.1\ \mathrm{m} 	imes 0.05\ \mathrm{m} 	imes 0.03\ \mathrm{m}$$ floats in water. What is the density of the wood?

Accepted Answer

$$333\ \mathrm{kg/m^3$}$$

Question 4

A spherical piece of plastic of radius $$10\ \mathrm{cm}$$ and density $$750\ \mathrm{kg/m^3$} is $$completely submerged in water and held by a string. What is the tension in the string?

Accepted Answer

$$2.5\ \mathrm{N}$$

Question 5

Water flows through a pipe that has a radius of $$5\ \mathrm{cm}$$ and the water has a speed of $$2\ \mathrm{m/s}. $$What is the volume flow rate of the water in the pipe?

Accepted Answer

$$0.016\ \mathrm{m^3$/s}$$

Question 6

A liquid with a density of $$1200\ \mathrm{kg/m^3$}$$ flows through two horizontal pipes. In the first section, the radius is $$0.1\ \mathrm{m}$$ and the speed is $$2\ \mathrm{m/s}. In $$the second section, the radius is $$0.05\ \mathrm{m}. $$What is the speed of the fluid in the second pipe?

Accepted Answer

$$8\ \mathrm{m/s}$$

Question 7

A liquid with a density of $$1200\ \mathrm{kg/m^3$}$$ flows through two horizontal pipes. In the first section, the radius is $$0.1\ \mathrm{m}$$ and the speed is $$2\ \mathrm{m/s}. In $$the second section, the radius is $$0.05\ \mathrm{m}. $$What is the pressure difference between the two sections?

Accepted Answer

$$-36,000\ \mathrm{Pa}$$

Question 8

The power of a train whistle is $$3\ \mathrm{W}$$ and the sound intensity at a distance of $$10\ \mathrm{m} is $$measured. What is the sound intensity?

Accepted Answer

$$2.4 	imes 10$$^{-3}$$\ \mathrm{W/m^2$}$$

Question 9

The sound from a jackhammer has a sound intensity level of $$90\ \mathrm{dB} at a $$distance of $$30\ \mathrm{m}. $$What is the sound intensity?

Accepted Answer

$$1.0 	imes 10$$^{-3}$$\ \mathrm{W/m^2$}$$

Question 10

An ambulance travels down the highway at $$33.3\ \mathrm{m/s}$$, its siren emits a sound of frequency $$900\ \mathrm{Hz}. $$What is the frequency heard by a stationary observer in front of the ambulance? (Speed of sound $$v = 343\ \mathrm{m/s})$$

Accepted Answer

$$990\ \mathrm{Hz}$$

Question 11

A semi-truck has a horn with a frequency of $$1000\ \mathrm{Hz}. $$The semi-truck is moving to the right at $$25\ \mathrm{m/s}$$, and a car is $$25\ \mathrm{m/s}$$ behind the truck, moving in the same direction. What frequency is heard by the person in the car? (Speed of sound $$v = 343\ \mathrm{m/s})$$

Accepted Answer

$$1000\ \mathrm{Hz}$$

Question 12

Three point charges are placed at the corners of an equilateral triangle of side $$0.12\ \mathrm{m}$$. $$q_A = 2\ \mu\mathrm{C}$$, $$q_B = 2\ \mu\mathrm{C}$$, $$q_C = -4\ \mu\mathrm{C}. $$What is the total force (magnitude and direction) on $$q_C$$ due to the other two charges? (Use $$k_e = 9.0 	imes 10^9$\ \mathrm{N\cdot m^2$/C^2$$}$)

Accepted Answer

$$10\ \mathrm{N}$$, upward

Question 13

A rocket engine has a sound intensity level of $$120\ \mathrm{dB} at a $$distance of $$25\ \mathrm{m}. $$What is the sound intensity at this distance?

Accepted Answer

$$1.0\ \mathrm{W/m^2$}$$

Question 14

A block of wood with density $$350\ \mathrm{kg/m^3$}$$ floats in water. What fraction of the block's volume is submerged?

Accepted Answer

$$0.35$$

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