Which statement is true about an atom and an element?
a) an atom can be broken down into different substances and an element is formed when two or more atoms combine.
b) an atom is made of identical elements and an element retains all of the characteristics of a particular atom.
c)an atom is the smallest unit of matter and an element is a pure substance that is made of identical atoms.

Which two objects have the greatest gravitational force acting between them

Aball tossed vertically upward from the ground next to a building passes the bottom of a window 1.8 s after being tossed and passes the top of the window 0.20 s later. the window is 2.0 m high from top to bottom. what was the ball's initial velocity? the unit vector j^ is directed upward. how far is the bottom of the window from the launch position? how high does the ball rise above the launch position?

Which accurately compares concave and convex lenses?