Gravity- Gravity is the force by which a planet or other body draws objects toward its center.
Friction- Friction is the resistance to motion of one object moving relative to another.
Difference between mass and weight- mass is the amount of “matter” in a object while weight is the force exerted on an object by gravity.
Free fall- state of a body that moves freely in any manner in the presence of gravity.
Hope this helps...(´∩。• ᵕ •。∩`)