In a hydraulic-press operation, it is impossible for the
A) output displacement to exceed the input displacement.
B) force output to exceed the force input.
C) energy output to exceed the energy input.
D) output piston's speed to exceed the input piston's speed.
E) none of the above
Answer: C
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The gravitational force between two objects is proportional to
A) the distance between the two objects. B) the square of the distance between the two objects. C) the product of the masses of the two objects. D) the square of the product of the masses of the two objects. E) none of the above
Consider a vertical 20-cm-tall flat plate at 120°C suspended in a fluid at 100°C. If the fluid is being forced past the plate from above, estimate the fluid velocity for which natural convection becomes negligible (less than 10%) in: (a) mercury (b) air (c) water.
GIVEN
? A vertical flat plate suspended in a fluid
? Plate temperature (Ts) = 120°C
? Fluid temperature (T?) = 100°C
? Fluid is being forced past the plate from above
? Plate height (H) = 20 cm = 0.2 m
FIND
? The fluid velocity (U?) for which natural convection has a less than 10% effect in
(a) mercury (b) air (c) water
ASSUMPTIONS
? Steady state
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Tables 26, 28 and 13
Mean Life: The mean life (time constant) of radon-222 is 5.526 d. If a sample of radon initially contains 6.00 × 108 radon atoms, how many of them are left after 10.0 d?
A. 9.82 × 107 B. 7.67 × 107 C. 8.34 × 108 D. 7.29 × 108 E. 8.56 × 108
Which of the following is not true about potential energy?
a. Potential energy is stored energy. b. Potential energy is related to position. c. Potential energy is a scalar quantity. d. Potential energy has direction.