Chapter 2: Newtonian Mechanics Flashcards
Force
- vector quantity
- experienced as a pushing or pulling on objects
- units: N (1N = kgm/s^2)
Mass vs. Weight
Mass = measure of a body's inertia (amount of matter in something; the body's tendency to resist changes in its velocity); scalar quantity; unit = kg Weight = measure of the gravitational force on an object's mass; vector quantity; unit = N
Equation for weight:
W = mg
Acceleration
- the rate of change of velocity that an object experiences as a result of some applied force
- unit = m/s^2
Newton’s Laws of Motion
- F = ma = 0; a body either at rest or in motion with constant velocity will remain that way unless a net force acts upon it
- SummationF = ma, in terms of components, SummationF(x) = ma(x) and SummationF(y) = ma(y); no acceleration of an object with mass, m, will occur when the vector sum of the forces results in a cancellation of those forces
- F(B) = -F(A); law of action and reaction; for every force exerted by object B on object A, there is an equal but opposite force exerted by object A on object B
Normal force
The force that is always perpendicular to the surface, exerted by the surface on the object that is resting upon it
Gravity
- attractive force felt by all forms of matter
- magnitude of gravitational force between two objects:
F = [Gm(1)m(2)]/(r^2)
G = 6.67 x 10^-11 Nm^2/kg^2
Different kinds of motion: Translational motion
- occurs when forces cause an object to move without any rotation about a fixed point in that object
Different kinds of motion: Rotational motion
- occurs when forces are applied against an object in such a way as to cause the object to rotate around a fixed pivot point (fulcrum); the application of force at some distance from the fulcrum generates torque
Rotational motion: Torque (definition and equations)
-Torque: generated when a force is applied to an object at some distance from the fulcrum, causes an object to move with rotational motion
T = rFsinø
Different kinds of motion: Circular motion
- occurs when forces cause an object to move in a circular pathway
- uniform circular motion: instantaneous velocity vector is always tangent to the circular path
- centripetal force (radial force) generates centripetal acceleration, this acceleration keeps the object in its circular pathway
F(c) - (mv^2)/r
a(c) = v^2/r
Forces of friction
-Friction: kind of force (electromagnetic) that works to oppose the movement of objects; almost always oppose an object’s motion and cause it to slow down or become more stationary
-Static friction (Fs): exists between a stationary object and the surface upon which it rests
0 µkFn always; it is harder to start an object moving than it is to keep the object moving
Mechanical equilibria: Translational equilibrium
- exists only when the vector sum of all the forces acting on an object is zero; also known as the first condition of equilibrium; when resultant force is zero, the object will not accelerate (meaning constant speed and constant direction)
- Note: this does not mean that the velocity is zero, it simply states that the velocity is constant
Mechanical equilibria: Rotational equilibrium
- exists only when the vector sum of all the torques acting on an object is zero; also known as the second condition of equilibrium; either the lever arm is not rotating at all or it is rotating with a constant angular frequency
