Exam 2 Content

average velocity = instantaneous velocity & average acceleration = instantaneous acceleration

when time is infinitesimally small (when time approaches 0s), velocity and acceleration are this

ax = 0m/s² and ay = g = 9.80m/s²

kinematics variables we know the values of for projectile motion

45°

the angle that gives the maximum possible range in a projectile motion problem

Newton’s First Law of Motion

an object continues in a state of rest or in a state of motion at a constant velocity (constant speed in constant direction), unless compelled to change that state by a net force

net force

the vector sum of all forces acting on an object; can be split into two dimensions (x and y)

Newton’s Second Law of Motion

when a net external force ΣF acts on an object of mass m, the acceleration a that results is directly proportional to the net force and has a magnitude that is inversely proportional to the mass—the direction of acceleration is the same as the direction of the net force (aka ΣF = ma)

free-body diagram

a diagram that represents an object and the forces that act on it; only forces that act on the object appear in the diagram

Newton’s Third Law of Motion

whenever one object exerts a force on a second object, the second object exerts an oppositely directed force of equal magnitude on the first object

F = G * m₁m₂/r²

Newton’s Law of Universal Gravitation

6.674 × 10⁻¹¹ N * m²/kg²

the universal gravitational constant

weight (W)

the gravitational force that the earth exerts on an object; is always acting downward toward the center of the earth and the magnitude is equal and opposite to the normal force

1. W = mg

2. W = G m(earth)m/r(earth)²

two equations for weight

normal force

a force that a surface exerts on an object with which it is in contact; the magnitude is equal and opposite to the weight

friction

a force parallel to the surface an object is on that occurs when an object attempts to move along a surface; is opposite in direction to the velocity

Fr = μFn (friction = coefficient of static friction * normal force)

friction equation

equilibrium

when an object has zero acceleration; the object is moving at a constant velocity AND whatever direction has 0 acceleration will have a net force of 0N