Which is NOT true about a protostar?
a. It is usually much larger than it will be as a star. b. It glows due to the heat of the gases in its core. c. It may become a brown dwarf. d. It generates pressure by fusing hydrogen.

How does the image distance (di) of a convex lens compare with the image distance of a concave lens? a. the image distance of the convex lens is positive, and that of the concave lens is negative. b. both are negative for a virtual image. c. both are positive for a virtual image d. the image distance of the convex lens is negative, and that of the concave lens is positive.

The law of the conservation of momentum says that the total momentum of any closed and isolated system cannot

The total amount of energy contained in an object