Q: A 500 kg hot-air balloon (excluding hot air) has a volume of $$1200\ \mathrm{m}^3. If $$the density of air is $$1.29\ \mathrm{kg/m}^3$$, what is the buoyant force on the balloon?

$$1.52 \times 10^4$\ \mathrm{N}$$

Q: A point source produces intensity $$I_1 = 2.0$$ \times $$10^{-6}$$\ \mathrm{W/m}^2$$ at r_1$ = 5.0\ \mathrm{m}. $$What is the power output of the source?

$$6.3 \times 10$$^{-5}$$\ \mathrm{W}$$

Question 1

A solid object floats in water with exactly half its volume submerged. What is the density of the object compared to the density of water?

Accepted Answer

It is half the density of water.

Question 2

Water flows from a wide pipe into a narrow pipe at the same height. According to Bernoulli's principle, what happens to the pressure in the narrow pipe?

Accepted Answer

The pressure is lower because water is faster.

Question 3

A mass on a spring oscillates on a frictionless surface. As the mass passes through equilibrium moving to the right, what is its acceleration?

Accepted Answer

Zero

Question 4

Two waves of equal amplitude and frequency travel in opposite directions on a string. What is the result?

Accepted Answer

A standing wave with nodes and antinodes

Question 5

Sound intensity from a point source decreases as $$1/r^2. If $$you move from $$2\ \mathrm{m} to$$ $$6\ \mathrm{m}$$ from the source, by what factor does the intensity decrease?

Accepted Answer

By a factor of 9

Question 6

An open organ pipe and a closed organ pipe have the same length $$L. $$What is the ratio of their fundamental frequencies ($$f_{open}:f_{closed}$$)?

Accepted Answer

$$2:1$$

Question 7

A mass on a spring has amplitude $$A. If $$the amplitude is doubled and the mass is quadrupled (spring constant unchanged), what happens to the period?

Accepted Answer

It is unchanged.

Question 8

A pendulum clock keeps perfect time on Earth. On a planet where $$g is $$four times larger, how does the clock run?

Accepted Answer

Twice as fast

Question 9

A tuning fork held near a guitar string causes the string to resonate. This demonstrates which phenomenon?

Accepted Answer

Forced resonance at the string's natural frequency

Question 10

Which factor does NOT affect the wave speed on a stretched string?

Accepted Answer

Amplitude of the wave

Question 11

A 500 kg hot-air balloon (excluding hot air) has a volume of $$1200\ \mathrm{m}^3. If $$the density of air is $$1.29\ \mathrm{kg/m}^3$$, what is the buoyant force on the balloon?

Accepted Answer

$$1.52 	imes 10^4$\ \mathrm{N}$$

Question 12

A large open tank has a hole $$3.00\ \mathrm{m}$$ below the water surface. Using Torricelli's theorem, what is the exit speed of water from the hole? ($$g = 9.8\ \mathrm{m/s}^2)$$

Accepted Answer

$$7.67\ \mathrm{m/s}$$

Question 13

A guitar string ($$\mu = 3.00 	imes 10$$^{-3}$$\ \mathrm{kg/m}$$, $$L = 0.650\ \mathrm{m}) is $$tuned to middle C ($$f_1 = 261.6$$\ \mathrm{Hz}$$). What is the wave speed on the string?

Accepted Answer

$$340\ \mathrm{m/s}$$

Question 14

A point source produces intensity $$I_1 = 2.0$$ 	imes $$10^{-6}$$\ \mathrm{W/m}^2$$ at r_1$ = 5.0\ \mathrm{m}. $$What is the power output of the source?

Accepted Answer

$$6.3 	imes 10$$^{-5}$$\ \mathrm{W}$$

Question 15

A closed pipe ($$L = 0.500\ \mathrm{m}) at$$ $$20^\circC ($$speed of sound $$= 343\ \mathrm{m/s}). $$What is the frequency of the first overtone?

Accepted Answer

$$1029\ \mathrm{Hz}$$

Question 16

A transverse wave is described by $$y(x,t) = (0.0300\ \mathrm{m}) \cos(4.00x - 120t). $$What is the wavelength?

Accepted Answer

$$1.57\ \mathrm{m}$$

Question 17

A buoy bobs in simple harmonic motion with amplitude $$A = 1.50\ \mathrm{m}$$ and period $$T = 8.00\ \mathrm{s}. $$What is the maximum speed of the buoy?

Accepted Answer

$$1.18\ \mathrm{m/s}$$

Question 18

A block ($$m = 1.50\ \mathrm{kg}) on a $$frictionless $$30.0^\circ$$ incline is held by a spring ($$k = 200\ \mathrm{N/m}) $$parallel to the incline. What is the equilibrium spring compression $$x_{eq}$$?

Accepted Answer

$$0.075\ \mathrm{m}$$

Question 19

A wave pulse moves right on a string fixed at the right end. When it reaches the end, what happens to the reflected pulse?

Accepted Answer

It is inverted (flipped upside down).

Question 20

Increasing the damping coefficient of an oscillator causes the oscillation frequency to:

Accepted Answer

Decrease slightly compared to undamped

Physics 2010 Final Practice: Step-by-Step Guidance for Fluids, Oscillations & Waves

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