What does our galaxy look like?
A.) It has a large disk with spiral arms, and is relatively flat and thin.
B.) It has clouds of gas and dust in the spiral arms.
C.) Older yellow stars are found mostly in the central bulge.
D.) Old stars and globular clusters are located in a spherical halo above and below the disk.
E.) All of the above
Ans: E.) All of the above
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A 4.0-kg aluminum block is originally at 10°C. If 160 kJ of thermal energy is added to the block, what is its final temperature? The specific heat capacity of aluminum is 910 J/kg ? K
A) 24°C B) 34°C C) 44°C D) 54°C
Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well insulated 10-gallon tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for analysis.
GIVEN - Two electric resistance heaters with l=0.2 m and d=0.02 m - V=10 gallon= 37.85 liter of water at T0 =300 K - Each heater power= 500 W FIND (a) Time required for bringing water temperature in the tank to Tf =340 K. (b) State the assumption for analysis. ASSUMPTIONS - Steady state heat transfer - All the heat dissipated through the heater is gained by water. - There is uniform mixing of fluid maintaining same temperature at each point at given time. PROPERTIES AND CONSTANTS Specific heat(cp)= 4177 J/(kg K) Density(?) = 989 kg/m3