Which statement describes the speed of a planet traveling in an elliptical orbit around the sun? . a. the speed is constant. b. the speed varies, but not with respect to its distance from the sun. c. the speed is slowest when it is farthest away from the sun. d. the speed varies

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 2 options: the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the cold balloon expands and rises. the warm balloon shrinks and sinks. the warm balloon expands and rises. the cold balloon shrinks and sinks.

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?

In a hydrogen molecule there are a total of four charges, 2 protons in the two nuclei, and 2 electrons. how many unique charge-pairs are there (without double counting)?