# PHY440 Mechanics, Waves and Thermal Physics

PHY440 Mechanics, Waves and Thermal Physics

Text book: Jewett, J.W. and Serway, R.A. (2010). Physics for Scientists and Engineers with Modern

Physics, 8th Edition, Brooks/Cole Cengage Learning.

Assignment 4

Question / Topic / Problem1 /

**Section 14.1 Pressure**/

**No 2 (Softcopy) p.423; No 4 (Hardcopy) p. 423**

2. The nucleus of an atom can be modeled as several

protons and neutrons closely packed together. Each particle

has a mass of 1.67 1027kg and radius on the order

of 1015m. (a) Use this model and the data provided to

estimate the density of the nucleus of an atom. (b) Compare

your result with the density of a material such as iron.

What do your result and comparison suggest concerning

the structure of matter?

2 /

**Section 14.3 Pressure Measurements**/

**No 21 (Softcopy) p.425; No 21 (Hardcopy) p. 425**

21. Mercury is poured into a U-tube as shown in Figure

P14.21a. The left arm of the tube has cross-sectional area A1

of 10.0 cm2, and the right arm has a cross-sectional area A2

of 5.00 cm2. One hundred grams of water are then poured

into the right arm as shown in Figure P14.21b. (a) Determine

the length of the water column in the right arm of the

U-tube. (b) Given that the density of mercury is 13.6 g/cm3,

what distance h does the mercury rise in the left arm?

3 /

**Section 14.4 Buoyant Forces and Archimedes’s Principle**/

**No 22 (Softcopy) p.425; No 26 (Hardcopy) p. 426**

22. A light balloon is filled with 400 m3 of helium at atmospheric

pressure. (a) At 0°C, the balloon can lift a payload

of what mass? (b) What If? In Table 14.1, observe that the

density of hydrogen is nearly half the density of helium.

What load can the balloon lift if filled with hydrogen?

4 /

**Section 14.4 Buoyant Forces and Archimedes’s Principle**/

**No 24 (Softcopy) p.425; No 24 (Hardcopy) p. 425**

24. The gravitational force exerted on a solid object is 5.00 N.

When the object is suspended from a spring scale and submerged

in water, the scale reads 3.50 N (Fig. P14.24). Find

the density of the object.

5 /

**Section 14.6 Bernoulli’s Equation**/

**No 42 (Softcopy) p.427; No 40 (Hardcopy) p. 427**

42. Water falls over a dam of height h with a mass flow rate

of R, in units of kilograms per second. (a) Show that the

power available from the water is

P = Rgh

where g is the free-fall acceleration. (b) Each hydroelectric

unit at the Grand Coulee Dam takes in water at a rate of

8.50 105kg/s from a height of 87.0 m. The power developed

by the falling water is converted to electric power

with an efficiency of 85.0%. How much electric power does

each hydroelectric unit produce?

6 /

**Section 16.3 The Speed of Waves on Strings**/

**No 21 (Softcopy) p.484; No 40 (Hardcopy) p. 427**

21. An Ethernet cable is 4.00 m long. The cable has a mass of

0.200 kg. A transverse pulse is produced by plucking one

end of the taut cable. The pulse makes four trips down and

back along the cable in 0.800 s. What is the tension in the

cable?

7 /

**Section 20.2 Specific Heat and Calorimetry**/

**No 6 (Softcopy) p.592; No 2 (Hardcopy) p. 592**

6. The temperature of a silver bar rises by 10.0°C when it

absorbs 1.23 kJ of energy by heat. The mass of the bar is

525 g. Determine the specific heat of silver from these

data.

8 /

**Section 20.2 Specific Heat and Calorimetry**/

**No 9 (Softcopy) p.593; No 11 (Hardcopy) p. 593**

9. A 1.50-kg iron horseshoe initially at 600°C is dropped into

a bucket containing 20.0 kg of water at 25.0°C. What is the

final temperature of the water–horseshoe system? Ignore

the heat capacity of the container and assume a negligible

amount of water boils away.

9 /

**Section 20.3 Latent Heat**/ No 16 (Softcopy) p.593; No 20 (Hardcopy) p. 594

16. A 3.00-g lead bullet at 30.0°C is fired at a speed of 240 m/s

into a large block of ice at 0°C, in which it becomes embedded.

What quantity of ice melts?

10 / Section 20.6 Some Applications of the First Law

of Thermodynamics / No 35 (Softcopy) p.595; No 35 (Hardcopy) p. 595

35. An ideal gas initially at Pi, Vi,

and Ti is taken through a cycle

as shown in Figure P20.35.

(a) Find the net work done on

the gas per cycle for 1.00 mol

of gas initially at 0°C. (b) What

is the net energy added by heat

to the gas per cycle?

11 / Section 20.6 Some Applications of the First Law

of Thermodynamics / No 37 (Softcopy) p.595; No 37 (Hardcopy) p. 595

37. A 1.00-kg block of aluminum is warmed at atmospheric

pressure so that its temperature increases from 22.0°C to

40.0°C. Find (a) the work done on the aluminum, (b) the

energy added to it by heat, and (c) the change in its internal

energy.

1