A protostar's radius decreases by a factor of 100 and its surface temperature increases by a factor of two before it becomes a main sequence star. Its luminosity: A. Decreases by a factor of 160,000 B. Decreases by a factor of 625 C. Decreases by a factor of 40 D. Increases by a factor of 40 E. Increases by a factor of 625 F. Increases by a factor of 160,000

So then we see that the final luminosity decrease by a factor of 625 so then the correct answer for this case would be:

B. Decreases by a factor of 625

Explanation:

For this case we can use the formula of luminosity in terms of the radius and the temperature given by:

Where L_i = initial luminosity, r= radius and T = temperature.

We know that we decrease the radius by a factor of 100 and the temperature increases by a factor of 2 so then the new luminosity would be:

So then we see that the final luminosity decrease by a factor of 625 so then the correct answer for this case would be:

B. Decreases by a factor of 625

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.