When you step on the bathroom scale, you exert a force on the scale. The force you apply to the scale compresses a spring, which moves the needle. When you throw a baseball, you apply a force to the ball, which makes it speed up. An airplane engine creates a force, which pushes the plane through the air. A car's tires exert a force on the ground, which pushes the car along.
Force causes acceleration .
This may sound simple, but it is a very important fact. The movement of the car is governed by Isaac Newton's Second Law , which forms the foundation for classical mechanics. To honor Newton's achievement, the standard unit of force in the SI system was named the newton . In fact, this is really how force and mass are defined. This gravity force is often referred to as g in equations.