a.

Gamma rays

b.

Alpha particles

c.

Wave particles

d.

Beta particles

a.

When accelerating, the resultant force acting on it must be equal to zero

b.

There must always be a non zero force acting on it

c.

At a steady velocity, the resultant force acting on it must be equal to zero

d.

At a steady velocity, the air resistance must be equal to zero

a.

volume

b.

mass

c.

thickness

d.

density

a.

Thickest at the top

b.

thickest at the middle

c.

thickest at the bottom

d.

of the same thickness throughout