Physics: Forces

force: an interaction that changes or tries to change the motion of an object

constant forces: arise from physical interactions between objects

externally applied forces: applied directly by an external agent to an object

friction: a force that forbids the motion between two surfaces

tension: force transmitted through a rope or cable when pulled

normal force: the force, which is perpendicular, exerted by a surface to support the weight of an object, like a table holding up a lamp

gravitational force: the pull the Earth exerts on objects, keeping them grounded and governing planetary orbits

electromagnetic force: the force between charged particles responsible for magnetism and electricity

nuclear forces: forces within the atomic nucleus, like the strong nuclear force that keeps the nucleus from falling apart

Newton’s first law: a body at rest remains at rest or, if in motion, continues moving at a constant velocity unless acted on by a net external force

• intertia!!

  • the natural tendency of objects to keep doing what they’re doing

Newton’s second law: the object’s acceleration is proportional to the net force and inversely proportional to its mass

• F = ma

translational equilibrium: when the forces are applied in a straight line

rotational equilibrium: when the forces rotate the object around its center

when an elevator accelerates upward, the floor must push up with more force than gravity to increase its velocity. this increases the normal force, making you feel heavier

during downward acceleration, the floor pushes up with less force than gravity because it slows you down

Newton’s third law: for every action, there is an equal and opposite reaction

• this is always the case for the internal forces of one system; they are opposite couples balancing each other