1)In a Merry-Go-Round the rotation curve is straight line with a positive slope

ID: 291712 • Letter: 1

Question

1)In a Merry-Go-Round the rotation curve is straight line with a positive slope (curve goes upward), this indicates that

a.in a Merry-Go-Round objects closer to the center move at a higher speed.

b.in a Merry-Go-Round objects closer to the center move at a slower speed.

c.in a Merry-Go-Round objects closer to the center take more time to complete an “orbit”.

d.in a Merry-Go-Round objects closer to the center take less time to complete an “orbit”.

2)The mass of Jupiter can be calculated by

knowing the Sun's mass and measuring the average distance of Jupiter from the Sun.

measuring the orbital period and distance of one of Jupiter's moons.

knowing the Sun's mass and measuring how Jupiter's speed changes during its elliptical orbit around the Sun.

d. measuring the orbital period and distance of Jupiter's orbit around the Sun.

3) What do we mean when we say that the rotation curve for a spiral galaxy is "flat"?

All the galaxy's mass is concentrated in its flat, gaseous disk.

The amount of light emitted by stars at different distances is about the same throughout the galaxy.

The disk of a spiral galaxy is quite flat, rather than being spherical like the halo.

Gas clouds orbiting far from the galactic center have approximately the same orbital speed as gas clouds located further inward

4)Spiral galaxy rotation curves are generally fairly flat out to large distances. Suppose that spiral galaxies did not contain dark matter. How would their rotation curves be different?

The rotation curve would be a straight, upward sloping diagonal line, like the rotation curve of a merry-go-round.

The rotation curve would look the same with or without the presence of dark matter.

The orbital speeds would rise upward with increasing distance from the galactic center, rather than remaining approximately constant.

The orbital speeds would fall off sharply with increasing distance from the galactic center.

5) Why do we think that most of the mass of the Milky Way may be in the form of dark matter?

The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo.

Our view of distant galaxies is sometimes obscured by dark blotches in the sky, and we believe these blotches are dark matter located in the halo.

Theoretical models of galaxy formation suggest that a galaxy cannot form unless it has at least 10 times as much matter as we see in the Milky Way disk, suggesting that the halo is full of dark matter.

d. Although dark matter emits no visible light, it can be seen with radio wavelengths, and such observations confirm that the halo is full of this material.

6)Based on observational evidence, is it possible that dark matter doesn’t really exist?

Yes, only if there is something wrong with our current understanding on how gravity should work on large scales.

Yes, but only if all the observations themselves are in error.

None of the above.

No, the evidence is too strong to think it could be in error.