URGENT!! Please ;-; Planet Y has twice the mass of Earth. An astronaut visits Planet Y and observes that his weight is half his weight on Earth. What is the radius of Planet Y? Let R = Earth's radius)

A. R

B. 2R

C. 4R

D. 0.5R

Ateam of astronauts is on a mission to land on and explore a large asteroid. in addition to collecting samples and performing experiments, one of their tasks is to demonstrate the concept of the escape speed by throwing rocks straight up at various initial speeds. with what minimum initial speed vesc will the rocks need to be thrown in order for them never to "fall" back to the asteroid? assume that the asteroid is approximately spherical, with an average density p 3.84 x108 g/m3 and volume v 2.17 x 1012 m3 recall that the universal gravitational constant is g 6.67 x 10-11 n m2/kg2

Lymphocytes known as blastocysts make antibodies that fight infection. select the best answer from the choices provided t f

Which best represents the law of conservation of mass ?