Are sunspots really dark and cool?
What will be an ideal response?
No, they are about 4,000 K, orange in color, but still cooler and darker than the bright yellow photosphere that surrounds them.
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Starting from rest, a proton falls through a potential difference of 1.2 kV. What speed does it acquire?
What will be an ideal response?
Two equal point charges are separated by a distance d. When the separation is reduced to d/4, what happens to the force between the charges?
A. it decreases by a factor of 4 B. it increases by a factor of 4 C. it increases by a factor of 8 D. it increases by a factor of 16 E. it increases by a factor of more than 16
An astronaut in a space suit is motionless in outer space. The propulsion unit strapped to her back ejects some gas with a velocity of 40.0 m/s. The astronaut recoils with a velocity of 1.00 m/s. If the mass of the astronaut and space suit after the gas is ejected is 100 kg and the mass of the gas ejected is 2.50 kg, then the total kinetic energy after the ejection of the gas is
A. 2,050 J. B. 3,430 J. C. 4,150 J. D. 5,070 J. E. 6,320 J.
What was there just after the Big Bang?
A) nothing B) the primeval fireball C) a singularity D) a black hole E) everything was inside Earth