Motion And Force Flashcards
Vector
Physical quantity with both magnitude and direction.
How to add vectors
Place the first vector such that the head of the arrow meets the tail of the second vector, and draw an arrow from the tail of the first to the head of the second.
How to subtract vectors
Place the heads of the two vectors together and draw an arrow from the tail of the first to the tail of the second.
Component vectors
Always at right angles to each other, and their sum is equal to the vector being replaced.
Pythagorean theorem
A2+B2=C2
SOH CAH TOA
Opp=Hsin(angle)
Adj=Hcos(angle)
Translational motion
Speed=distance/time Velocity =displacement/time Acceleration =change in velocity/time X-Xo=Vot+1/2at2 V-Vo=at V2=Vo2+2a(X-Xo) Vavg =1/2(V+Vo)
Scalar
Physical quantity that has magnitude but no direction.
Displacement vs time graph
Slope = instantaneous velocity at that time.
Upward slope = positive velocity; downward slope = negative velocity (velocity in the reverse direction)
Straight line = constant velocity (straight horizontal line = slope of 0 = not moving). Curved line = changing velocity = acceleration.
Area beneath curve has no meaning.
Velocity vs time graph
Slope = instantaneous acceleration at that time.
Upward slope = positive acceleration; downward slope = negative acceleration (acceleration in the reverse direction).
Straight line = constant acceleration; curved line = changing acceleration.
Area beneath curve = distance (label all area between curve and zero velocity as positive) or displacement (label area below zero velocity as negative)
Gravitational acceleration
~10 m/s2
Projectile motion
Initial vertical velocity (or Vo sin angle) is equal to the square root of 2gh, where g is positive 10 m/s2 and h is peak height. Can also use this equation to find final velocity v of a projectile that is dropped straight down from a height h.
Mass does not affect projectile motion assuming that there is no air resistance.
Inertia
The tendency of all objects to remain in their current state of motion, whether they are moving or at rest.
Mass
Quantitative measure of an object’s inertia; how much that object will resist a change in its motion. Usually measured in kg.
Weight
Gravitational force that an object experiences when it is close to a much larger body, such as the earth. Measured in newtons (N).
Weight at surface of earth = mg
Center of mass
Point at which all of the system’s mass can be considered to be concentrated. Center of mass of an object doesn’t have to be located within that object.
Net force
The sum of all forces acting on an object. Two forces that are equal in magnitude but opposite in direction will cancel each other out, leaving zero net force.
Net force, think acceleration.
Force
Causes and changes motion. Four types of force in nature: strong nuclear force; weak nuclear force; gravitational force; electromagnetic force. First two exist only within nucleus of an atom.
Contact forces are electromagnetic.
Newton’s first law of motion
Inertia
Newton’s second law of motion
F=ma, F and a are directly proportional.
Newton’s third law of motion
For every action, there exists an equal and opposite reaction
Newton’s law of universal gravitation
F=G(m1m2/r2) where G=6.67x10-11 m3kg-1s-2.
Inclined planes
Normal force equals mg cos (angle).
Net force due to gravity and the normal force equals mg sin (angle) and is parallel to the plane.
Friction
Force that opposes relative motion.
Common type of friction is drag, aka air resistance.
More massive objects are less affected by air resistance than less massive objects.
Hooke’s law
Applies to compression or stretching an object.
F=-k (change in position), where k is a constant unique to a given object.
Most often applied to springs.
