Principle purpose of this lecture is to present on Mass, Force and Gravity. Mass–Amount of stuff (atoms/molecules) in an object. Measured in kg. Force – Measures the gravitational pull on something. Measured in N (newtons). Earths Gravitational Field Strength – 10N/kg. (The gravitational field strength at the surface of the Earth produces a force of approximately 10 N on every mass of 1 kg). Every object in universe that has mass exerts a gravitational pull, or force, on every other mass. The size of the pull depends on the masses of the objects.