Which of the following statements is incorrect?
What will be an ideal response?
Solar output has decreased slightly, causing cooling (FALSE)
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A square silicone chip 7 mm by 7 mm in size and 0.5 mm thick is mounted on a plastic substrate as shown in the sketch below. The top surface of the chip is cooled by a synthetic liquid flowing over it. Electronic circuits on the bottom of the chip generate heat at a rate of 5 watts that must be transferred through the chip. Estimate the steady state temperature difference between the front and back surfaces of the chip. The thermal conductivity of silicone is 150 W/(m K).
GIVEN
A 0.007 m by 0.007 m silicone chip
Thickness of the chip (L) = 0.5 mm = 0.0005 m
Heat generated at the back of the chip (Gq) = 5 W
The thermal conductivity of silicon (k) = 150 W/(m K)
FIND
The steady state temperature difference (?T)
ASSUMPTIONS
One dimensional conduction (edge effects are negligible)
The thermal conductivity is constant
The heat lost through the plastic substrate is negligible
SKETCH
A 12,000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of unequal areas, filled with incompressible oil with a density of 800 kg/m3 and capped at both ends with tight-fitting pistons
The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the same level. What is the force that must be applied to the smaller piston in order to lift the car after it has been raised 1.20 m? (For purposes of this problem, you can neglect the weight of the pistons.) A) 0.954 kN B) 1.88 kN C) 1.96 kN D) 3.67 kN E) 1.20 kN
In comparing first magnitude Deneb with second magnitude Polaris, we find that
A) Polaris is in reality much more luminous. B) Deneb must be much hotter than Polaris. C) Deneb appears 2.5 times brighter to us than does Polaris. D) Polaris is really 100 times brighter than nearby Deneb. E) Deneb is really much closer than Polaris.
The gravitational force is a conservative force
Indicate whether the statement is true or false