GRAVITY Chapter 12.2

Introduction Even though we can’t see gravity, it is a constant and fundamental force that determines the motion of all objects here on Earth. When NASA scientists explore our solar system, they need to take careful measurements of gravitational forces to ensure that orbiting satellites and land rovers will function properly.

Gravity Gravity might seem like common sense, but how does gravity work? Gravity is the fundamental force of attraction between all objects in the universe. We often think of gravity as a “pulling” force, that holds us to Earth, but in reality weight is an attraction that is measured by acceleration.

Gravity Gravity causes all objects to fall at a specific acceleration, for this reason gravity is measured in m/s2. Earth’s gravity is 9.8 m/s2. All objects fall toward Earth’s surface with the same acceleration. No matter if it is a penny or a hippopotamus or a skateboarder…

Gravity Whether two objects are very large or very small, there is still gravity between them. Every object has its own gravitational force. Even drops of water or a paper clip have gravity, they are just so small that it is not noticeable.

Gravity Gravity is much easier to detect with bigger objects like planets. The bigger the object, the bigger its gravitational force. We could compare the gravitational forces of the different planets and see this is true.

Gravity Bigger objects have bigger gravitational attraction. Imagine trying to lift an house or trying to lift a mouse using only balloons. The hamster would only need a few balloons based on its size. But a house would need…

Gravity Gravity decreases as the distance between objects increase. The farther apart the objects are, the less they are affected by each other’s distances. The closer the objects are, the greater their gravitational attraction.

Gravitational force is weak between objects that have small masses. Gravitational force is stronger when one or both objects are larger. Gravitational force rapidly becomes weaker as the distance between the two masses increases.

Weight vs. Mass Easy to confuse, but BIG difference Mass is the amount of matter in an object. Mass is measured in grams. Mass is ALWAYS the same. The force of an object due to gravity is known as weight. Because weight is a force it is measured in Newtons (N).

Weight vs. Mass Because gravity is an acceleration, and our body has mass, we can calculate our weight by substituting gravity for acceleration in the equation and substituting weight for force. W=mg

Weight vs. Mass Because weight is affected by gravity, weight is relative to the surface we stand on. Weight changes depending on the gravity. • What is the weight of a 2 kg mass? 1960 N 320 N 740 N