Moon phase question

Two separate pairs of binary stars are observed. The separation of the pairs is identical, but the orbital period of Pair X is 4 times the orbital period of Pair Y

How does the total mass of the stars in Pair X compare to the total mass of the stars in Pair Y? A) Pair X has a total mass 2 times greater than Pair Y. B) Pair Y has a total mass 2 times greater than Pair X. C) Pair Y has a total mass 16 times greater than Pair X. D) Pair X has a total mass 16 times greater than Pair Y.

If a 20-kg object dropped in air has a terminal speed of 60 m/s, what was its acceleration at 30 m/s?

a. 9.80 m/s2 b. 7.35 m/s2 c. 4.90 m/s2 d. 2.45 m/s2 e. More information is needed to answer this question.

A heavy sled and a light sled, both moving horizontally with the same speed, suddenly slide onto a rough patch of snow and eventually come to a stop

The coefficient of kinetic friction between the sleds and the rough snow is the same for both of them. Which of the following statements about these sleds are correct? (There could be more than one correct choice.) A) The friction from the snow will do more negative work on the heavy sled than on the light sled. B) The light sled will slide farther on the rough snow than the heavy sled. C) The heavy sled will slide farther on the rough snow than the light sled. D) Both sleds will slide the same distance on the rough snow before stopping. E) The friction from the snow will do the same amount of work on both sleds.

In their common rest frame, two stars are 90.0 light-years (ly) apart. If they are 12.0 ly apart as measured by the navigator in a spaceship traveling between them, how fast is the spaceship moving? Express your answer in terms of c

A) 0.991c B) 0.986c C) 0.980c D) 0.972c