Which of these is a pure substance?

a. cake mix
b. ocean water
c. 10 carat gold
d. solid gold

What properties of a moving object are used in determining the object's energy of motion

If a simple machine reduces the strength of a force, what must be increased?

If two students are running down the hall toward each other, trying to get to class, and they have the same mass and acceleration, what will happen when they collide? will their forces cancel out or will each one experience a reaction?