Mechanics Review Concepts Flashcards
Position
X - (scalar) the location of an object relative to a chosen origin.
Displacement
Change in X - (vector) from initial position to its current position. Change in X = Current position - Initial Position
Distance
S - magnitude of displacement or total path length
Velocity
V - (vector) ratio of displacement to time. If the change in t is very small, V is considered to be instantaneous. If the change in t is not small, V is an average velocity.
Speed
(scalar) magnitude of velocity. average V = change in v/ time
Acceleration
a - (vector) the ratio of the change of an object’s velocity, change in v, to time.
System
Collection of objects in a process
Enviroment
Objects outside of the system
Force
F - (vector) push or pull between 2 objects that characterizes their interaction.
Force Diagrams (Free Body Diagrams)
Represent all forces on an object or system. Use trig to split x vs y. x or y axis should be in the plane of motion.
Newton’s 1st Law
An object with velocity maintains it without change.
Newton’s 2nd Law
(F/m)=a. (F/m)=(change in v)/t. F * t =M*(change in v). Impulse = change in momentum
Newton’s 3rd Law
2 objects exert equal magnitude and opposite direction forces of the same type on each other.
Gravitational Force
(vector) all objects have gravitational fields. 2 objects must be present.
Static Friction
F(s) - (vector) force of friction on an object not sliding on the surface. F(s)=Mu(s)*F(n)
Kinetic Friction
F(k) - (vector) Mu(k) depends on both surfaces, involves sliding, doesn’t change. F(k)=Mu(k)*F(n)
Projectile Motion
Net force is Fg due to earth. Horizontal motion: change in x= V(x)*t. All kinematic equations: a=g.
Uniform Circular Motion
Perfect circle. (sum)F is pointed center. a is pointed center. change in V is pointed center. V is tangential to the circle.
Collision in an isolated system
(sum)F=0. Kinetic energy isn’t guaranteed to be conserved. Mass conserved.
Linear Momentum
P - (vector) the product of mass*velocity. Describes an object’s state. Total momentum of a system is the sum of all momentum of all objects in the system.
Impulse
J - (vector) product of the average force exerted on the object during the time interval change in t. J=Ft
Generalized Momentum Impulse Theorem
The change in momentum in the system = external impulse. When J=0, the momentum of the system stays constant.
Work
W - (scalar) a way to change the energy of a system. Done by external forces W = Fdcos(theta). Depends on the Force, direction of motion, and the angle between them.
Gravitational Potential Energy
Ug - (scalar) energy of a system due to the relative separation of 2 objects. Change in Ug=mg*change in y.
Kinetic Energy
KE - (scalar) energy of motion depends on m and v. KE=(1/2)mv^2
Elastic Potential Energy
Us =(1/2)Kx^2, energy stored in a compressed or stretched spring.
Total Mechanical Energy
TME= Ug + Us + K(T) + K(R)
Work-Energy Theorem
Work= change in TME = change in k. No work: change in Ug +Us + K(T) + K(R) =change in Ug’ +Us’ + K(T)’ + K(R)’. Work= change in Ug +Us + K(T) + K(R) + W = change in Ug’ +Us’ + K(T)’ + K(R)’.
Elastic Collisions
P and change in KE are constant
Inelastic Collisions
P is constant, and KE decreases.
Totally Inelastic Collisions
Stick Together
Power
(change in E)/t = W/t. 1 Watt = 1 J/s
Center of Mass
The point at which we can consider all of the gravitational force to be exerted. An external force facing directly towards or away from the center of mass won’t cause rotation.
Torque
T - (vector) physical quantity characterizing the turning ability of a force with respect to a particular axis of rotation.
Rotational Intertia
Physical quantity I=kmr^2. Depends on mass distribution. Describes an object’s rotation.
Rotational Momentum
Conserved just like P. L=I(omega). change in L = torque * t
