Which list gives the correct numbers of subatomic particles for a neutral atom of helium? O A. Two protons, two neutrons, two electrons O B. Two protons, two neutrons, four electrons O C. Two protons, four neutrons, six electrons O D. Four protons, four neutrons, four electrons

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

Suppose a comet has an orbital period of 309.1 years around the sun. what is it’s average distance from the sun?

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.