Life cycle of a star question i don't feel like answering by
1on of the endings of a star that has a mass 4-8 times greater than our sun; are very dense
2this is what a low or medium life star will become later in its life; typically have the same mass as our sun, but only a bit larger than the earth
3the explosion of a star when it has reached the end of its lifetime; are no longer stars, and are seen as bright points of light in the sky

How does the space charge width change with forward and reverse bias? also, calculate the space charge width for a reverse bias of 4v on a silicon pn junction at t = 300k and doping concentrations of na = 5x1015cm-3 , nd = 5x 1016 cm-3 .

The image shows a pendulum in simple harmonic motion the pendulum starts at a and swing to e

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.