Example Problems from
Chapter 9 & 10Chapter 9 & 10
First slide: problem
Second slide: solution
Bone has a Young's modulus of about
1.80 1010 Pa. Under compression, it can
withstand a stress of about 1.50 108 Pa
before breaking. Assume that a femur
(thigh-bone) is 0.40 m long, and (thigh-bone) is 0.40 m long, and
calculate the amount of compression
this bone can withstand before breaking.
A wooden block of volume 5.24 10-4 m3 floats in
water, and a small steel object of mass m is placed
on top of the block. When m = 0.370 kg, the system
is in equilibrium and the top of the wooden block is
at the level of the water.
(a) What is the density of the wood? (a) What is the density of the wood?
(b) What happens to the block when the steel
object is replaced by a second steel object with a
mass less than 0.370 kg? What happens to the
block when the steel object is replaced by yet
another steel object with a mass greater than
0.370 kg?
(a) Calculate the mass flow rate (in grams
per second) of blood (ρ = 1.0 g/cm3) in
an aorta with a cross-sectional area of
2.0 cm2 if the flow speed is 33 cm/s.
(b) Assume that the aorta branches to
form a large number of capillaries with a
combined cross-sectional area of 3.0 103
cm2. What is the flow speed in the
capillaries?
On a day when the temperature is 20°C,
a concrete walk is poured in such a way
that its ends are unable to move. (a)
What is the stress in the cement when its
temperature is 50°C on a hot, sunny day? temperature is 50°C on a hot, sunny day?
(b) Does the concrete fracture? Take
Young's modulus for concrete to be 7.00
109 N/m2 and the compressive strength
to be 2.00 107 N/m2.
An air bubble has a volume of 1.30
cm3 when it is released by a
submarine 115 m below the surface
of a lake. What is the volume of the
bubble when it reaches the surface? bubble when it reaches the surface?
Assume the temperature and the
number of air molecules in the
bubble remain constant during its
ascent.
The rms speed of an oxygen
molecule (O2) in a container of
oxygen gas is 721 m/s. What is the oxygen gas is 721 m/s. What is the
temperature of the gas?
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