(100 points!) A star of radius R1 rotates every 20 days. The star suddenly collapses to a radius R2, which is smaller by a factor of 10000 (R2=R1/10000) without losing mass.

a. What is the new angular velocity of the star? You may assume that the moment of inertia of the star is that of a solid sphere (I=(2/5)mR^2)?

b. What is the ratio of the kinetic energy before and after the collapse (KEf/KEi)?

Describe how the fermi level changes with donor level, temperature and contact with p and n type semiconductors

Iwill give 30 points to whoever answers ! what is the formula for actual mechanical advantage and ideal mechanical advantage?

Aball is thrown from the top of a building with an initial velocity of 21.9 m/s straight upward, at an initial height of 51.6 m above the ground. the ball just misses the edge of the roof on its way down, as shown in the figure. (a) determine the time needed for the ball to reach its maximum height. (b) determine the maximum height. (c) determine the time needed for the ball to return to the height from which it was thrown, and the velocity of the ball at that instant. (d) determine the time needed for the ball to reach the ground. (e) determine the velocity and position of the ball at t = 5.35 s.