What is the difference between mass and weight? Physical processes -Force and motion - Gravity Learning Points Mass is the amount of stuff in an object, it is measured in grams and kilograms. The force of gravity acting on an object is called weight. Weight is measured in newtons. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.