Decreasing the focal length of the eyepiece in a compound microscope by 50% changes the magnification to _______ times the previous magnification.
A. 0.50
B. 1.5
C. 1.7
D. 2.0
E. 4.0
D. 2.0
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Which of the following stars spends the longest time in the protostellar phase of life?
A) a 1 solar-mass star B) a 2 solar-mass star C) a 3 solar-mass star D) a 4 solar-mass star E) a 5 solar-mass star
Which forces have physicists shown to be the same force under conditions of very high temperature, as confirmed by experiments in particle accelerators?
A) the electromagnetic and weak forces B) gravity and the strong force C) the strong and electromagnetic forces D) the strong and weak forces E) gravity and the weak force
In a large chemical factory, hot gases at 2273 K are cooled by a liquid at 373 K with gas side and liquid side convection heat transfer coefficients of 50 and 1000 W/(m2 K), respectively. The wall that separates the gas and liquid streams is composed of 2-cm thick slab of stainless steel on the liquid side. There is a contact resistance between the oxide layer and the steel of 0.05 m2.K/W. Determine the rate of heat loss from hot gases through the composite wall to the liquid.
GIVEN
FIND
Rate of heat loss from hot gases through composite wall to liquid.
ASSUMPTIONS
- 1 Dimensional steady state heat transfer
- Thermal conductivity remain constant.
- Radiation is negligible.
SKETCH
Which of the following reaction energies is the least exothermic (but still an exothermic reaction)?
A) 540 kJ/mole B) -540 kJ/mole C) 125 kJ/mole D) -125 kJ/mole E) not enough information given