Why are sound waves not used to communicate between objects in space?

Drug abuse will not lead to physical and psychological dependence. true or false ?

What is the correct equation for cellular respiration?

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?