A flea is able to jump about 0.5 m. It has been said that if a flea were as big as a human, it would be able to jump over a 100-story building! When an animal jumps, it converts work done in contracting muscles into gravitational potential energy (with some steps in between). The maximum force exerted by a muscle is proportional to its cross-sectional area, and the work done by the muscle is this force times the length of contraction. If we magnified a flea by a factor of 1 000, the cross section of its muscle would increase by 1 000 2 and the length of contraction would increase by 1 000. How high would this “superflea” be able to jump? (Don’t forget that the mass of the “superflea" increases as well.)
A flea is able to jump about 0.5 m. It has been said that if a flea were as big as a human, it would be able to jump over a 100-story building! When an animal jumps, it converts work done in contracting muscles into gravitational potential energy (with some steps in between). The maximum force exerted by a muscle is proportional to its cross-sectional area, and the work done by the muscle is this force times the length of contraction. If we magnified a flea by a factor of 1 000, the cross section of its muscle would increase by 1 000 2 and the length of contraction would increase by 1 000. How high would this “superflea” be able to jump? (Don’t forget that the mass of the “superflea" increases as well.)
Solution Summary: The author explains the Work-Energy theorem for the jump of the original flea.
A flea is able to jump about 0.5 m. It has been said that if a flea were as big as a human, it would be able to jump over a 100-story building! When an animal jumps, it converts work done in contracting muscles into gravitational potential energy (with some steps in between). The maximum force exerted by a muscle is proportional to its cross-sectional area, and the work done by the muscle is this force times the length of contraction. If we magnified a flea by a factor of 1 000, the cross section of its muscle would increase by 1 0002 and the length of contraction would increase by 1 000. How high would this “superflea” be able to jump? (Don’t forget that the mass of the “superflea" increases as well.)
A cylinder with a piston contains 0.153 mol of
nitrogen at a pressure of 1.83×105 Pa and a
temperature of 290 K. The nitrogen may be
treated as an ideal gas. The gas is first compressed
isobarically to half its original volume. It then
expands adiabatically back to its original volume,
and finally it is heated isochorically to its original
pressure.
Part A
Compute the temperature at the beginning of the adiabatic expansion.
Express your answer in kelvins.
ΕΠΙ ΑΣΦ
T₁ =
?
K
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Part B
Compute the temperature at the end of the adiabatic expansion.
Express your answer in kelvins.
Π ΑΣΦ
T₂ =
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Part C
Compute the minimum pressure.
Express your answer in pascals.
ΕΠΙ ΑΣΦ
P =
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?
?
K
Pa
Learning Goal:
To understand the meaning and the basic applications of
pV diagrams for an ideal gas.
As you know, the parameters of an ideal gas are
described by the equation
pV = nRT,
where p is the pressure of the gas, V is the volume of
the gas, n is the number of moles, R is the universal gas
constant, and T is the absolute temperature of the gas. It
follows that, for a portion of an ideal gas,
pV
= constant.
Τ
One can see that, if the amount of gas remains constant,
it is impossible to change just one parameter of the gas:
At least one more parameter would also change. For
instance, if the pressure of the gas is changed, we can
be sure that either the volume or the temperature of the
gas (or, maybe, both!) would also change.
To explore these changes, it is often convenient to draw a
graph showing one parameter as a function of the other.
Although there are many choices of axes, the most
common one is a plot of pressure as a function of
volume: a pV diagram.
In this problem, you…
Learning Goal:
To understand the meaning and the basic applications of
pV diagrams for an ideal gas.
As you know, the parameters of an ideal gas are
described by the equation
pV = nRT,
where p is the pressure of the gas, V is the volume of
the gas, n is the number of moles, R is the universal gas
constant, and T is the absolute temperature of the gas. It
follows that, for a portion of an ideal gas,
pV
= constant.
T
One can see that, if the amount of gas remains constant,
it is impossible to change just one parameter of the gas:
At least one more parameter would also change. For
instance, if the pressure of the gas is changed, we can
be sure that either the volume or the temperature of the
gas (or, maybe, both!) would also change.
To explore these changes, it is often convenient to draw a
graph showing one parameter as a function of the other.
Although there are many choices of axes, the most
common one is a plot of pressure as a function of
volume: a pV diagram.
In this problem, you…
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