Force
Reference from the original Physics I textbook.
- Force
A physical phenomena that can modify the acceleration of some object.
- Related Glossary Terms
Force Equation, Free body diagrams↗, Newton’s First Law, Newton’s Second Law, Normal Forceⓘ, Spring Force, Spring Force Equation, Tension, Vector, Weight, Work
- Index
Chapter 1 - Newton’s Laws and FBDs
Glossary and deeper reading · 2 refreshers
These editorial refreshers supplement the reading. Definitions and examples are added guidance; original source wording and recorded answers remain in their original context.
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Free-body diagram
A free-body diagram shows the external forces acting on one selected object or system. Each arrow names a real interaction, and its direction is the direction of that force. For example, a book resting on a desk has a downward gravitational force and an upward normal force; velocity is not an extra force arrow.
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Normal force
A normal force is a contact force perpendicular to the local surface of contact. Its magnitude is set by the motion and the other forces, so it need not equal the object’s weight. For example, a wall’s normal force on a leaning ladder points horizontally rather than upward.