Why is the number of galaxies in the Local Group uncertain?

What will be an ideal response?


The total number of galaxies in the Local Group is uncertain because some galaxies lie in the plane of the Milky Way Galaxy and are difficult to detect.

Physics & Space Science

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A solenoid 4.0 cm in radius and 4.0 m in length has 8 000 uniformly spaced turns and carries a current of 5.0 A. Consider a plane circular surface (radius = 2.0 cm) located at the center of the solenoid with its axis coincident with the axis of the solenoid. What is the magnetic flux through this surface? (1 Wb = 1 T ? m2)

a. 63 ?Wb b. 16 ?Wb c. 0.25 mWb d. 10 ?Wb e. 5.0 ?Wb

Physics & Space Science

A 3.0-?F capacitor charged to 40 V and a 5.0-?F capacitor charged to 18 V are connected to each other, with the positive plate of each connected to the negative plate of the other. What is the final charge on the 3.0-?F capacitor?

A. 11 ?C B. 15 ?C C. 19 ?C D. 26 ?C E. 79 ?C

Physics & Space Science

Which of these nuclei has the least mass?

A) hydrogen B) iron C) lead D) uranium E) all the same

Physics & Space Science

An electron and a proton, are released simultaneously from rest and start to move towards each other because of the attractive Coulomb force between them. They are initially separated by a distance d. The two particles eventually collide

When they collide, A) they are closer to the electron's initial position. B) they are at the midpoint of their initial separation. C) they are closer to the proton's initial position. D) Not enough data is given to predict where they collide.

Physics & Space Science