Which of the following protogalactic clouds is most likely to form an elliptical galaxy?
A) a very low-density cloud with very little angular momentum
B) a dense cloud with very little angular momentum
C) a low-density cloud with quite a bit of angular momentum
D) a very massive cloud with any density and a lot of angular momentum
B) a dense cloud with very little angular momentum
You might also like to view...
The model we have constructed in this chapter neglects feedback effects that might accelerate or brake the warming. Scientists now predict that the Arctic Ocean will be ice-free in the summer by as early as 2020 (due to increased temperatures in the Arctic). Less ice will mean that the Arctic will reflect less visible light back into space. Will this accelerate or brake the warming compared to the predictions of the model in the text?
A. Accelerate B. Brake C. No change
Heat transfer from an electronic circuit board is to be determined by placing a model for the board in a wind tunnel. The model is a 15-cm-square plate with embedded electrical heaters. The wind from the tunnel air is delivered at 20°C. Determine the average temperature of the model as a function of power dissipation for an air velocity of 2.5 and 10 m/s. The model is pitched 30° and yawed 10° with respect to the flow direction. The surface of the model acts as a blackbody.
GIVEN
• A Model square electronic circuit board pitched 30° and yawed 10° in a wind tunnel
• Length of a side (L) = 15 cm = 0.15 m
• Air temperature (T?) = 20°C = 293 K
• Air velocity (U?) = 2.5 m/s or 10 m/s FIND
• The average surface temperature of the model (Ts) as a function of power dissipation (Q )
ASSUMPTIONS
Steady state
The surface of the model acts as a black body (? = 1.0)
The wind tunnel acts as a black body enclosure at the air temperature.
SKETCH
If the value of H is doubled, it would also double the age of the universe
Indicate whether the statement is true or false
A 10 kg meteor moves through outer space, far from all gravitational influences. How much work is done on the meteor during a 5 m segment of its path?
A) none B) 50 J C) 2 J D) 20 J E) 500 J