PLATE NO. 7
Equilibrium, Fluid Mechanics
and Temperature
NAME
SUBJECT CODE – COURSE/YEAR/SECTION
PHYSICS LECTURE SCHEDULE AND TIME
Rating:
_________________________
DIRECTIONS: For each item, copy the problem first before solving it. State the given
and required values. Draw a figure if needed. Box your final answers. Write legibly. No
erasures.
1. The 21,500 g light is suspended on a 12,000 g beam
(labeled AB) that has a length of 720 cm. At point A,
there is reaction force acting on the joint. The
reaction force has horizontal and vertical
components. Find the a) tension in the CD line and b)
horizontal and vertical component of the reaction
force at point A.
2. Determine the tension in the cables that supports the
33000 g light.
3. A 1700000 g object is hanging from the end of a steel beam with a cross-sectional
area of 0.012 square meters. Determine the beam’s a) stress, b) strain, and c) elongation
of the beam if it has a length of 950 cm. Ysteel = 200 x 109 Pa.
4. A steel wire has a diameter of 0.06 cm and has a length of 200 cm. Determine the
change in length when the steel wire is subjected to load of 90 Newtons. Y = 20 X 1010
Pa.
5. An air tube is used to fill up a room with air every 720 seconds. If the air tube has a
diameter of 30 cm and the room has a dimension of 820 cm by 500 cm by 350 cm, what
is the velocity of the air in the tube?
6. Determine the lift in Newtons of a wing that has an area of 88 square meters and is
flying at a certain altitude. The air flows over the top surface at a speed of 0.28 km/s and
0.15 km/s over the bottom surface.
7. An airfoil flying at the following conditions: P = 101325 Pa and ρ = 1.225 kg/m3. If the
pressure at a given point on the airfoil is 90000 Pa, determine the velocity at this
location.
8. Convert the following Kelvin temperatures to the Celsius and Fahrenheit scales: (a)
the midday temperature at the surface of the moon (400 K); (b) the temperature at the
tops of the clouds in the atmosphere of Saturn (95 K): (c) the temperature at the center
of the sun (1.55 X 107 K).
9. Aluminum rivets used in airplane construction are made slightly larger than the rivet
holes and cooled by “dry ice” (solid CO2) before being driven. If the diameter of a hole is
4.500 mm. What should be the diameter of a rivet at 23.0°C if its diameter is to equal
that of the hole when the rivet is cooled to -78.0°C, the temperature of dry ice? The
expansion coefficient remains constant at the value of 2.4 X 10-5 /°C.
10. In an effort to stay awake for an all-night study session, a student makes a cup of
coffee by first placing a 200-W electric immersion heater in 0.320 kg of water, (a) How
much heat must be added to the water to raise its temperature from 20.0°C to 80.0°C?
(b) How much time is required? Assume that all of the heater’s power goes into heating
the water. The specific heat capacity of the water is 4190 J/ kg K.
ANSWER KEY. DO NOT COPY THIS PART INTO YOUR PLATE.
1. a) 408.08 N, b) 408.08 N and 328.52 N
2. 194.76 N and 258.46 N
3. a) 1.389 X 106 Pa, b) 6.945 X 10-6 and c) 6.598 x 10-5 m
4. 0.318 cm
5. 2.8 m/s
6. 3013010 N
7. 144.8786 m/s
8. a) 260 F b) -289 F c) 2.79 X 107 F
9. 4.511 mm
10. t = 6.7 min