What is the meaning of friend ?​

Aregion of space in which a measurable gravitational force is indicated by the force exerted on a test mass is called

Alead ball is dropped into a lake from a diving board 5m above the water . it hits the water with a certain velocity and then sink with constant velocity in bottom . it reaches the bottom 5 second after it is dropped if g= 10m/s2 . find depth of the lake and average velocity of the ball ?

Hydrogen and helium are both members of?