Homework
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A piano string sounds a middle A by vibrating
primarily at 220 Hz.
(a) Calculate the string's period and angular
frequency.
(h) Calculate the period and angular frequency for
a soprano singing an A one octave higher, which is
twice the frequency of the piano string.
Solution
Homework
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A harmonic oscillator consists of a 0.500-kg mass
attached to an ideal spring with force constant 140
N/m. Find (a) the period; (h) the frequency; (c) the
angular frequency of the oscillations.
Solution
Homework
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An object is undergoing SHM with period 1.200 s
and amplitude 0.600 m. At t = 0 the object is at x
= O. How far is the object from the equilibrium
position when t = 0.480 s
Solution
Homework
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Weighing Astronauts. This procedure has actually
been used to "weigh" astronauts in space. A 42.5kg chair is attached to a spring and allowed to
oscillate. When it is empty, the chair takes 1.30 s to
make one complete vibration. But with an astronaut
sitting in it, with her feet off the floor, the chair
takes 2.54 s for one cycle. What is the mass of the
astronaut .
Solution
Homework
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A 1.50-kg mass on a spring has displacement as a
function of time given by the equation
x(t) = (7.40 cm)cos[(4.16 S-l)t - 2.42].
Find (a) the time for one complete vibration;
(b) the force constant of the spring;
(c) the maximum speed of the mass; (d) the maximum force on the mass; (e) the position, speed, and
acceleration of the mass at t = 1.00 s; (f) the force
on the mass at that time.
Solution
Homework
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13.23. A 0.500-kg glider, attached to the end of
an ideal spring with force constant k = 450 N/m,
undergoes SHM with an amplitude of 0.040 m.
Compute (a) the maximum speed of the glider; (b)
the speed of the glider when it is at x = -0.015 m;
(c) the magnitude of the maximum acceleration of
the glider; (d) the acceleration of the glider at x =
-0.015 m; (e) the total mechanical energy of the
glider at any point in its motion.
Solution
Homework
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13.26. A 0.150-kg toy is undergoing SHM on the
end of a horizontal spring with force constant k =
300 N/m. When the object is 0.0120 m from its
equilibrium position, it is observed to have a speed
of 0.300 m/s. What are (a) the total energy of the
object at any point of its motion; (b) the amplitude
of the motion; (c) the maximum speed attained by
the object during its motion?
Solution
Homework
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13.31. A l75-g glider on a horizontal, frictionless
air track is attached to a fixed ideal spring with
force constant 155 N/m. At the instant you make
measurements on the glider, it is moving atO.815
m/s and is 3.00 cm from its equilibrium point. Use
energy conservation to find (a) the amplitude of the
motion and (b) the maximum speed of the glider. (c)
What is the angular frequency of the oscillations.
Solution
Solution
Homework
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13.41- You pull a simple pendulum 0.240 m long to
the side through an angle of 3.50 and release it. (a)
How much time does it take the pendulum bob to
reach its highest speed. (b) How much time does it
take if the pendulum is released at an angle of
1.750 instead of 3.50 .
Solution
Homework
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13.47- After landing on an unfamiliar planet, a
space explorer constructs a simple pendulum of
length 50.0 cm. She finds that the pendulum makes
100 complete swings in 136s. What is the value of
g on this planet .
Solution
Homework
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43.22- Radioactive isotopes used in cancer therapy
have a "shelf- life," like pharmaceuticals used in
chemotherapy. Just after it has been manufactured
in a nuclear reactor, the activity of a sample of 60co
is 5000 Ci. When its activity falls below 3500 Ci, it
is considered too weak a source to use in treatment.
You work in the radiology department of a large
hospital. One of these 60co sources in your inventory
was manufactured on October 6, 2004. It is now
April 6, 2007. Is the source still usable? The half-life
of 60co is 5.271 years.
Solution
Homework
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43.23, A 12.0-g sample of carbon from living
matter decays at the rate of 180.0 decays/min due
to the radioactive 14c in it. What will be the decay
rate of this sample in (a) 1000 years and (b)
50,000 years?
Solution
Homework
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43.24, Radioactive Tracers. Radioactive isotopes are
often introduced into the body through the bloodstream.
Their spread through the body can then be monitored
by detecting the appearance of radiation in different
organs. 131I, β- emitter with a half- life of 8.0 d is one
such tracer. Suppose a scientist introduces a sample with
an activity of 375 Bq and watches it spread to the
organs. (a) Assuming that the sample all went to the
thyroid gland, what will be the decay rate in that gland
24 d (about 21/2 weeks) later? (b) If the decay rate in
the thyroid 24 d later is actually measured to be 17.0
Bq, what percentage of the tracer went to that gland?
(c) What isotope remains after the 1-131 decays?
Solution
Homework
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4325. Tritium (3H) undergoes β- decay with a halflife of 12.3 years. It is also highly toxic to living
things. (a) What nucleus is produced in the β- decay
of tritium? (b) Suppose some tritium gas is released
into the atmosphere in a nuclear power plant
accident. How long will it take for 90.0% of the
tritium to become nonradioactive?
Solution
Homework
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43.26. As a health physicist, you are being
consulted about a spill in a radiochemistry lab. The
isotope spilled was 500µCi of 13IBa, which has a
half-life of 12 days. (a) What mass of I31Ba was
spilled? (b) Your recommendation is to clear the lab
until the radiation level has fallen 1.00µCi. How
long will the lab have to be closed?
Solution