If you read from left to right across a period in the periodic table, which statement is true?

a. the mass of the atoms increases.
b. the number of electrons decreases.
c. the properties of the elements are all roughly the same.
d. the elements are listed in the order they were discovered.

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?

Asolid cylinder and a cylindrical shell have the same mass, same radius, and turn on frictionless, horizontal axles. the cylindrical shell has light-weight spokes connecting the shell to the axle. a rope is wrapped around each cylinder and tied to blocks of equal masses that are held the same height above the ground. both blocks are released simultaneously. the ropes do not slip. which block hits the ground first? or is it a tie?

What is the increase in density of a medium due to wave travel?