Simplify the following text for a Grade 4 native English-speaking person.
Original: The normal force is one of the components of the ground reaction force and may coincide with it , for example considering a person standing still on the ground , in which case the ground reaction force reduces to the normal force . In another common situation , if an object hits a surface with some speed , and the surface can withstand it , the normal force provides for a rapid deceleration , which will depend on the flexibility of the surface .
Simplified: Normal force is the force that the ground ( or any surface ) pushes back up with .