Kinematics & Dynamics Flashcards
SI Units
Length = meter, Mass = kilogram, Time = second, Current = ampere (coulomb/second), Amount of a substance = moles, Temp = kelvin, Luminous Intensity = candela
Base unit
The standard units around which the system (SI) is designed
Derived unit
Associating base units with each other
Newton
Unit of force.
1 kg x m/s^2
Derived force unit
Newton
Derived work/energy unit
Joule
kg x m^2/s^2
Derived power unit
Watt
kg x m^2/s^3
Vectors
Numbers that have magnitude and direction
Displacement, velocity, acceleration, force
Scalars
Numbers that have magnitudes only and no direction
Distance, speed, energy, pressure, mass
Resultant
Sum or difference of two or more vectors
Pythagorean Theorem
X^2 + Y^2 = V^2
Component method
Used to find the Resultant. Add all X and Y sides together then use Pythagorean theorem to find resultant
Vector Subtraction
Can be accomplished by adding a vector with equal magnitude, but opposite direction, to the first vector.
A - B = A + (-B)
Dot product
Used to generate a scalar quantity from two vectors. The absolute values of A . B cos angle
Cross product
Used to generate a third vector like Torque.
The absolute values of A x B sin angle. The resultant of cross product is always perpendicular to the plane created by the two vectors
Displacement
Vector quantity that has both magnitude and direction, but does not account for the actual pathway taken between initial and final positions (a full circle would mean 0 displacement) x or d
v = change in x/change in time
v is average velocity, change in x is change in position
Distance
Scalar quantity that takes into account the pathway taken (italic d)
Velocity
A vector measured as the rate of change of displacement in a given unit of time, units are meters/second
Speed
Measured as the rate of actual distance traveled in a given unit of time
Instantaneous speed
Always equal to the magnitude of the object’s instantaneous velocity (v), which is the average velocity as the change in time approaches zero
Average speed
Measure of distance traveled in a given period of time
Average velocity
Measure of displacement of an object over a given period of time
Gravity
Attractive force felt by all forms of matter. acceleration due to gravity, g, decreases with height above the earth and increases the closer one gets to the Earth’s center of mass.. g = 10 m/s^2
Gravitational force
Fg = Gm1m2/r^2
Magnitude of gravitational force between two objects
r = distance between their centers of mass
G is universal gravitational constant (6.67 x 10^-11 N x m^2/kg^2)
*If r is halved, Fg will quadruple b/c force is inversely related to the square of distance.
*If m1 is tripled, then Fg will triple b/c mass is directly related to force
Friction
Type of force that opposes the movement of objects.
Two kinds: Static & Kinetic
Static friction
Exists between a stationary object and the surface upon which it rests.
f_s=µ_s N
µ_s is the coefficient of static friction
N = normal force
Normal force
component of the force between two objects in contact that is perpendicular to the plane of contact between the object and the surface upon which it rests.
Kinetic friction
Exists between a sliding object and the surface over which the object slides.
f_k=µ_k N
* the coefficient of static friction will always be larger than the coefficient of kinetic friction b/c it always requires more force to get an object to start sliding than it takes to keep an object sliding
Mass
Measure of a body’s inertia–the amount of matter in an object (kg is SI unit)
Weight
Measure of gravitational force. Fg w/ unit of Newton
Fg = mg where m is mass and g is acceleration due to gravity (9.8 m/s^2)
Translational equilibrium
Exists only when the vector sum of all of the forces acting on an object is zero
First condition of equilibrium
When the vector sum of all the forces acting on an object is zero
Zero acceleration means
Zero net force! This means tat any object with a constant velocity has no net force acting on it. However, just because the net force equals zero does not mean the velocity equals zero.
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). Torque (moment of force) happens at some distance from the fulcrum and is termed the lever arm
Rotational equilibrium
Exists only when the vector sum of all the torques acting on an object is zero.
Second condition of equilibrium
The vector sum of all torques acting on an object is zero
Clockwise rotation
Considered negative Torque
Counterclockwise rotation
Considered positive Torque
