PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HOMEWORK PROBLEMS Chapter 9:
SOLIDS AND FLUIDS
HW-9
PART-A: Hand in your answers in class on scantron on Monday 15 November-2010. Write your
name, class (1401) and HW # 9 on the scantron.
1. What is the mass of a solid gold rectangular bar that has dimensions of 4.50 cm x 11.0 cm x
26.0 cm?
(a) 24.8 kg
(b) 45.6 kg
(c) 11.4 kg
(d) 33.2 kg
(e) 19.5 kg
2. A 66.0-kg man lies on his back on a bed of nails, with 1 208 of the nails in contact with his
body. The end of each nail has area 1.00 x 10−6 m2. What average pressure is exerted by one nail
on the man’s body?
(a) 2.21 x 105 Pa
(b) 3.09 x 105 Pa
(c) 1.65 x 106 Pa
(d) 5.35 x 105 Pa
(e) 4.11 x 104 Pa
3. A hydraulic jack has an input piston of area 0.050 m2 and an output piston of area 0.70 m2.
How much force on the input piston is required to lift a car weighing 1.2 x 103 N?
(a) 42 N
(b) 68 N
(c) 86 N
(d) 110 N
(e) 130 N
4. A lead bullet is placed in a pool of mercury. What fractional part of the volume of the bullet is
submerged?
(a) 0.455
(b) 0.622
(c) 0.714
(d) 0.831
(e) 0.930
5. What is the pressure at the bottom of Loch Ness, which is as much as 754 ft deep? (The
surface of the lake is only 15.8 m above sea level; hence, the pressure there can be taken to be
1.013 x 105 Pa.)
(a) 1.52 X 105 Pa
(b) 2.74 X 105 Pa
(c) 2.35 X 106 Pa
(d) 7.01 X 105 Pa
(e) 3.15 X 105 Pa
6. Hurricane winds of 95 mi/h are blowing over the flat roof of a well-sealed house. What is the
difference in air pressure between the inside and outside of the house?
(a) 1.2 X 103 Pa
(b) 2.4 X 104 Pa
(c) 3.4 X 103 Pa
(d) 4.0 X 103 Pa
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(e) 5.3 X 10 Pa
7. A horizontal pipe narrows from a radius of 0.250 m to 0.100 m. If the speed of the water in the
pipe is 1.00 m/s in the larger-radius pipe, what is the speed in the smaller pipe?
(a) 4.50 m/s (b) 2.50 m/s (c) 3.75 m/s (d) 6.25 m/s (e) 5.13 m/s
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PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-9
8. Bernoulli’s equation can be used to explain, in part, which of the following phenomena?
(a) the lift on an airplane wing in flight
(b) the curve of a spinning baseball
(c) vascular flutter
(d) reduction in pressure of moving fluids
(e) all these answers
9. A boat develops a leak and, after its passengers are rescued, eventually sinks to the bottom of
a lake. When the boat is at the bottom, is the normal force on the boat
(a) greater than the weight of the boat,
(b) equal to the weight of the boat,
(c) less than the weight of the boat,
(d) equal to the weight of the displaced water, or
(e) equal to the buoyant force on the boat?
10. Three vessels of different shapes are filled to the same level with water as in Figure
MCQ9.10. The area of the base is the same for all three vessels. Which of the following
statements is valid?
(a) The pressure at the top surface of vessel A is greatest because it has the largest surface area.
(b) The pressure at the bottom of vessel A is greatest because it contains the most water.
(c) The pressure at the bottom of each vessel is the same.
(d) The force on the bottom of each vessel is not the same.
(e) At a given depth below the surface of each vessel, the pressure on the side of vessel A is
greatest because of its slope.
11. An ideal fluid flows through a horizontal pipe having a diameter that varies along its length.
Does the sum of the pressure and kinetic energy per unit volume at different sections of the pipe
(a) decrease as the pipe diameter increases, (b) increase as the pipe diameter increases,
(c) increase as the pipe diameter decreases, (d) decrease as the pipe diameter decreases, or
(e) remain the same as the pipe diameter changes.
12. A hose is pointed straight up, with water flowing from it at a steady volume flow rate and
reaching a maximum height of h. Neglecting air resistance, which of the following adjustments
to the nozzle will result in the water reaching a height of 4h?
(a) Decrease the area of the opening by a factor of 16.
(b) Decrease the area by a factor of 8.
(c) Decrease the area by a factor of 4.
(d) Decrease the area by a factor of 2.
(e) Give up because the water cannot reach a height of 4h.
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PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-9
13. When water freezes, it expands about 9.00%. What would be the pressure increase inside
your automobile engine block if the water in it froze? The bulk modulus of ice is 2.00 X 109
N/m2.
a. 1.65 x 107 Pa
b. 1.65 x 108Pa
c. 1.65 x 105 Pa
d. 1.65 x 105 Pa
14. A stainless-steel orthodontic wire is applied to a tooth, as in Figure P9.6. The wire has an
unstretched length of 3.1 cm and a diameter of 0.22 mm. If the wire is stretched 0.10 mm,
find the magnitude and direction of the force on the tooth. Disregard the width of the tooth
and assume Young’s modulus for stainless steel is 18 X 1010 Pa.
a.
b.
c.
d.
14 N
18 N
22 N
26 N
15. A large man sits on a four-legged chair with his feet off the floor. The combined mass of
the man and chair is 95.0 kg. If the chair legs are circular and have a radius of 0.500 cm at
the bottom, what pressure does each leg exert on the floor?
a. 2.96 x 106 Pa
b. 3.96 x 106 Pa
c. 2.46 x 106 Pa
d. 2.16 x 106 Pa
16. A hypodermic syringe contains a medicine with the density of water (Fig. P9.47). The
barrel of the syringe has a cross-sectional area of 2.50 X 10−5 m2. In the absence of a force on
the plunger, the pressure everywhere is 1.00 atm. A force of magnitude 2.00 N is exerted
on the plunger, making medicine squirt from the needle. Determine the medicine’s flow
speed through the needle. Assume the pressure in the needle remains equal to 1.00 atm and
that the syringe is horizontal.
a.
b.
c.
d.
11.6 m/s
12.6 m/s
13.6 m/s
14.6 m/s
17. On October 21, 2001, Ian Ashpole of the United Kingdom achieved a record altitude of
3.35 km (11 000 ft) powered by 600 toy balloons filled with helium. Each filled balloon had
a radius of about 0.50 m and an estimated mass of 0.30 kg. Estimate the net upward force on
all 600 balloons.
a. 1.5 N
b. 1.8 N
c. 2.2 N
d. 2.7 N
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