What occurrence defines the end of the protostar phase of a star's life and the start of the main-sequence phase?

Atoms in a stays in a fixed position I have no freedom to move

If the earth rotated on an axis that was not tilted, how would this affect the seasons?

A log splitting machine was invented to split logs quickly. A motor powers a metal piece that is pushed through the middle of a log. The metal piece used to split a log is an example of what simple machine? a. wedgeb. pulleyc. screwd. lever

A distant galaxy is determined to be 150 million light years distant and moving away from us; using the Hubble law determine its velocity in terms

A coil with a self-inductance of 3.0 H and a resistance of 100Ω carries a steady current of 2.0 A. (a) What is the energy stored in the magnetic field of the coil? (b) What is the energy per second dissipated in the resistance of the coil?

Which of the following elements is the most reactive? Beryllium Calcium Magnesium Barium

A flash of white light containing all the colors of the visible spectrum in air shines straight down on the surface of a pool.

A car accelerates uniformly from 0 to 15m/s in 5 s. Calculate acceleration.

Which device would a sleep researcher use to monitor a sleeping person's brain waves?

An experiment is performed to obtain the value of a physical property. If the true (i. e., correct) value of the property is 50 and the measured (i. e., experimental) value is 32, the percent error of the experimental result is: