Chapter 4: Forces and Newton’s Laws of Motion Glossary

the study of how forces affect the motion of objects and systems

a force acting on an object or system that originates outside of the object or system

a push or pull on an object with a specific magnitude and direction; can be represented by vectors; can be expressed as a multiple of a standard force; the SI unit of force is the Newton

a diagram showing all external forces acting on a body

a situation in which the only force acting on an object is the force of gravity

an external force that acts opposite to the direction of motion or, for when there is no relative motion, in the direction needed to prevent slipping

the tendency of an object at rest to remain at rest, or for a moving object to remain in motion in a straight line and at a constant speed

Newton’s first law of motion: a body at rest remains at rest or, if in motion, remains in motion at a constant speed in a straight line, unless acted on by a net external force; also known as the law of inertia

the quantity of matter in a substance; the SI unit of mass is the kilogram

the sum of all external forces acting on an object or system