Two objects undergo a collision, and there is no external force on the objects. This means that:
A. Both objects move at constant velocity
B. The objects have equal and opposite velocities
C. The center of mass moves with constant velocity
D. The center of mass is stationary
C. The center of mass moves with constant velocity
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A positive magnetic susceptibility is due to an applied magnetic field orienting electron _________in the direction of the applied magnetic field.
Fill in the blank(s) with the appropriate word(s).
Like our solar system, the whole Milky Way is about five billion years old
Indicate whether the statement is true or false
Increasing the amplitude of a mass-and-spring system causes what kind of change in the resonant frequency of the system? (Assume no other changes in the system.)
A) The frequency increases. B) The frequency decreases. C) There is no change in the frequency. D) The frequency depends on the displacement, not the amplitude.
An electric room heater has been designed in the shape of a vertical cylinder 2-m-tall and 30 cm in diameter. For safety, the heater surface cannot exceed 35°C. If the room air is 20°C, find the power rating of the heater in watts.
GIVEN
• An electric heater in the shape of a vertical cylinder
• Heater height (H) = 2 m
• Heater diameter (D) = 30 cm = 0.3 m
• Room air temperature (T?) = 20°C = 293 K
FIND
• The power rating of the heater (q) in watts
ASSUMPTIONS
• Radiation is negligible
• Heat transfer from the top and bottom of the tank is negligible
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 27.5°C
Thermal expansion coefficient (?) = 0.00332 1/K
Thermal conductivity (k) = 0.0256 W/(m K)
Kinematic viscosity (?) = 16.4 × 10–6 m2/s
Prandtl number (Pr) = 0.71