BBC
Bbc: Gcse Bitesize: Mass, Weight and Gravitational Field Strength
This lesson focuses on gravitational fields and includes what one is, the formula for gravity force, defining weight, formula for mass, an example of how to calculate gravity force, a practice question, and a link to a test.
CK-12 Foundation
Ck 12: Fifth Grade Science: Earth Science: Gravity
Do you know how gravity affects you? This module defines gravity and explains how gravity affects the motion of objects.