When a particle is a distance r from the origin, its potential energy function is given by the equation U(r) = kr, where k is a constant and r =
(a) What are the SI units of k?
(b) Find a mathematical expression in terms of x, y, and z for the y component of the force on the particle.
(c) If U = 3.00 J when the particle is 2.00 m from the origin, find the numerical value of the y component of the force on this particle when it is at the point (-1.00 m, 2.00 m, 3.00 m).
What will be an ideal response?
Answer: (a) kg ? m/s2 (or J/m or N) (b) Fy = - (c) -0.802 N
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An RLC series circuit has a 22 
resistor, a 3.0 H inductor, and a capacitor. What capacitance would result in resonance at 60 Hz?
A. 55 mF
B. 0.33 F
C. 65
F
D. 15 mF
E. 2.3
F
Contrast the atmosphere of Venus with its clouds
What will be an ideal response?
Water at 180°C enters a bare, 15-m-long, 2.5-cm wrought iron pipe at 3 m/s. If air at 10°C flows perpendicular to the pipe at 12 m/s, determine the outlet temperature of the water. (Note that the temperature difference between the air and the water varies along the pipe.)
GIVEN
• Wrought-iron pipe with water flow inside and perpendicular air flow outside
• Water entrance temperature (TW,in) = 180°C
• Water velocity (VW) = 3 m/s
• Pipe length (L) = 15 m
• Pipe diameter (D) = 2.5 cm = 0.025 m
• Air temperature (Ta) = 10°C
• Air velocity (Va) = 12 m/s FIND
• Outlet temperature of the water (TW,out) ASSUMPTIONS
• Steady state
• Air flow approaching pipe is negligible
• Thermal resistance of the pipe is negligible
• The pipe thickness can be neglected
SKETCH
A circuit consists of a 9.3-mH coil, a 16.0-V battery, a parallel combination of a 19-? resistor and a 6.0-? resistor, and a switch, all in series. What is the time constant of this circuit?
a. 3.7E–4 s b. 2.0E–3 s c. 4.9E–4 s d. 3.3E–2 s e. This circuit has 2 time constants.