Why did they scientists originally believe that the Sun was near the Milky Way's center?
Answer:
- The center of the Milky Way is not seen in visible light.
- Star counts appeared to be the same in all directions about the disk.
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What color are the star clusters in the spiral arms and what does that mean?
A.) Red and that means they are old. B.) Red and that means they have just formed recently. C.) Blue and that means they are old. D.) Blue and that means they have just formed recently. E.) Black and that means they are covered by dust.
Answer the following statement(s) true (T) or false (F)
1. A person who exerts a 100-N force horizontally in the +x direction on a wall for 10 minutes does positive work on the wall. 2. When an object slides down a frictionless incline, the contact interaction between the object and incline does no work on the object. 3. The interaction does not change the object’s kinetic energy. 4. The interaction does not change the object’s momentum. 5. A heavy ball swings at the end of a chain connected to a hook in the ceiling. Suppose I pull the ball away from its equilibrium position, hold it against my nose (with the chain taut), and then release the ball from rest. The ball swings away and then back toward my face. As long as I don’t move, and the ball is left alone, I can be confident that the ball will not smash my nose.
An observer approaches a stationary 1000 Hz sound source at twice the speed of sound. The observer hears a frequency of
A) 2000 Hz. B) 500 Hz. C) 4000 Hz. D) 1500 Hz. E) 3000 Hz.
The 500-m-long spaceship Springbrake is at rest on the planet Hitest for refueling. Another spaceship, Summerbrake, passes parallel to Springbrake at 0.600c. The crew on Springbrake measure the length of Summerbrake as it passes and find that the length they measure is exactly the same as the known 500-m rest length of Springbrake. If Summerbrake were at rest next to Springbrake, its length would
then be measured to be a. 180 m. b. 320 m. c. 500 m. d. 625 m. e. 781 m.