In general, what can be said about type O and B stars compared to type K and M stars?
A) They are hotter and younger.
B) They are cooler and older.
C) They are cooler and younger.
D) They are hotter and older.
E) They are neither hotter nor cooler, younger nor older.
A
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The unbalanced force acting on an object is zero. What is the direction and magnitude of the object's velocity and acceleration?
Centaurus A is a radio galaxy that has a visible galaxy at the center. This central elliptical galaxy of Centaurus A is encircled by a ring of gas and dust, different from most elliptical galaxies. The dust ring orbits about an axis that is perpendicular to the axis of rotation of the elliptical galaxy. What does this suggest about this central elliptical galaxy of Centaurus A?
a. The radio jets have caused the dust disk to be driven around the elliptical galaxy. b. There are at least two black holes at the center of the elliptical galaxy. c. Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy. d. Dust is produced as the jets interact with the intergalactic medium. e. Elliptical galaxies often contain dust that forms a disk along their rotation axis.
Consider the loop of flexible wire shown below. If we pass a current through the loop, will it tend to expand (becoming more circular), scrunch up even more tightly, or do nothing?
A. Expand
B. Scrunch up
C. Do nothing
D. The answer depends on the current’s direction.
A metal wire has a resistance of 25.00 W under room temperature conditions of 25°C. When the wire is heated to 85°C the resistance increases by 1.95 W. What is the temperature coefficient of resistivity of this metal?
a. 1.3 × 10^-3 (°C)-1 c. 5.0 × 10^-4 (°C)-1 b. 1.5 × 10^-3 (°C)-1 d. 2.5 × 10^-3 (°C)-1