5 Newton’s Laws of Motion
5 Chapter Review
Key Terms
- dynamics
- study of how forces affect the motion of objects and systems
- external force
- force acting on an object or system that originates outside of the object or system
- force
- push or pull on an object with a specific magnitude and direction; can be represented by vectors or expressed as a multiple of a standard force
- free fall
- situation in which the only force acting on an object is gravity
- free-body diagram
- sketch showing all external forces acting on an object or system; the system is represented by a single isolated point, and the forces are represented by vectors extending outward from that point
- Hooke’s law
- in a spring, a restoring force proportional to and in the opposite direction of the imposed displacement
- inertia
- ability of an object to resist changes in its motion
- inertial reference frame
- reference frame moving at constant velocity relative to an inertial frame is also inertial; a reference frame accelerating relative to an inertial frame is not inertial
- law of inertia
- see Newton’s first law of motion
- net external force
- vector sum of all external forces acting on an object or system; causes a mass to accelerate
- newton
- SI unit of force; 1 N is the force needed to accelerate an object with a mass of 1 kg at a rate of 1m/s21m/s2
- Newton’s first law of motion
- body at rest remains at rest or, if in motion, remains in motion at constant velocity unless acted on by a net external force; also known as the law of inertia
- Newton’s second law of motion
- acceleration of a system is directly proportional to and in the same direction as the net external force acting on the system and is inversely proportional to its mass
- Newton’s third law of motion
- whenever one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the force that it exerts
- normal force
- force supporting the weight of an object, or a load, that is perpendicular to the surface of contact between the load and its support; the surface applies this force to an object to support the weight of the object
- tension
- pulling force that acts along a stretched flexible connector, such as a rope or cable
- thrust
- reaction force that pushes a body forward in response to a backward force
- weight
- force w⃗ w→ due to gravity acting on an object of mass m
Key Equations
| Net external force | [latex]{\mathbf{\overset{\to }{F}}}_{\text{net}}=\sum \mathbf{\overset{\to }{F}}={\mathbf{\overset{\to }{F}}}_{1}+{\mathbf{\overset{\to }{F}}}_{2}+\cdots[/latex] |
| Newton’s first law | [latex]\mathbf{\overset{\to }{v}}=\,\text{constant when}\,{\mathbf{\overset{\to }{F}}}_{\text{net}}=\mathbf{\overset{\to }{0}}\,\text{N}[/latex] |
| Newton’s second law, vector form | [latex]{\mathbf{\overset{\to }{F}}}_{\text{net}}=\sum \mathbf{\overset{\to }{F}}=m\mathbf{\overset{\to }{a}}[/latex] |
| Newton’s second law, scalar form | [lat