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?