A ball at rest falls from a platform above the ground. The ball falls freely and hits the ground 3 s later. What is the height of the platform?
(use -9.8 m/s2 today for the acceleration due to gravity)

Sound is a disturbance that travels through a medium as a

Greg drew a diagram to compare two of the fundamental forces. which labels belong in the areas marked x, y and z? gravitational force electromagnetic force x. attractive y repulsive z: infinite range x: infinite range y attractive z. repulsive x. always attractive y: infinite range z: attractive or repulsive x. attractive or repulsive y infinite range z: always attractive

Convection currents are caused by differences in what two things?