Why is the main sequence main? Why are these stars so common?
What will be an ideal response?
While their masses, luminosities, and temperatures vary greatly, like the Sun, all of them are relatively young, with plenty of hydrogen still left to turn into helium in their cores. Hydrogen is still the most common element in the universe.
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Resolution: The pupil of a person's eye changes from a diameter of 3.5 mm to 1.5 mm as the illumination is increased. By what factor does the minimum angle of resolution change?
A. 0.43 B. 0.65 C. 2.0 D. 2.3
A heavy frog and a light frog jump straight up. They push off in such a way that they both have the same kinetic energy just as they leave the ground. Assume air resistance is negligible
Which of the following statements about these frogs are correct? (There could be more than one correct choice.) A) Just as they leave the ground, the heavier frog is moving faster than the lighter frog. B) Just as they leave the ground, the lighter frog is moving faster than the heavier frog. C) They both leave the ground with the same speed. D) The lighter frog goes higher than the heavier frog. E) The heavier frog goes higher than the lighter frog. F) Both frogs reach the same maximum height.
What holds Earth satellites up so they don't crash into Earth?
A) gravity B) centripetal force C) centrifugal force D) the absence of air resistance E) nothing, they continually fall fast enough around Earth not to crash
A steam turbine is an example of a heat mover
a. True b. False Indicate whether the statement is true or false