# Shared Flashcard Set

## Details

Momentum, Energy, and Waves
Unit 4
39
Physics
12/04/2011

Term
 Define Period
Definition
 The time interval between two successive occurrences of a recurrent event or phases of an event
Term
 Define frequency
Definition
 The number of times a specified periodic phenomenon occurs within a specified interval
Term
 define amplitude
Definition
 The maximum absolute value of a periodically varying quantity
Term
 define wavelength
Definition
 distance at which a wave repeats itself
Term
 define impulse
Definition
 The product obtained by multiplying the average value of a force by the time during which it acts. The impulse equals the change in momentum produced by the force in this time interval
Term
 define work
Definition
 transfer of energy from one physical system to another
Term
 define momentum
Definition
 a measure of how difficult it is to stop a moving object
Term
 define and give examples of transverse waves
Definition
 s waves--those waves whose direction is perpendicular to the disturbance producing it ex. light (3x10^8m/s)
Term
 define and give examples of longitudinal waves
Definition
 p waves--those whose direction is parallel to the disturbance producing itex. sound(344m/s)
Term
 Discuss resonance. give 3 examples.
Definition
 Resonance is defined as when a system is driven or pushed at its natural frequency the amplitude of oscillation grows very large, very fast. Ex. child on swing, troops over bridge, voice breaking a glass
Term
 Discuss how standing waves are produced
Definition
Term
 why do troops break step when crossing a bridge?
Definition
 Bc if their foot falls match the natural frequency of the bridge it will collapse
Term
 Why will sound not travel in a vacuum? Will light?
Definition
 This is because sound is the vibration of molecules, and there is nothing in a vacuum so there are no molecules to vibrate. Light can because it only needs eletric and magnetic fields to exist, and a vacuum has such fields.
Term
 A water wave has a wavelength of 12 cm and a speed of 50 cm/s. What is the wave's frequency?
Definition
 v=fλ
Term
 Discuss Fnet=ma vs Wnet=ΔKE
Definition
 The Wnet equation can be derived from the Fnet equation. The Wnet equation is the 1st enery theorem, and states that network is equal to change in energy due to an object's motion.
Term
 Define nodes and anti-nodes.
Definition
 A point or region of virtually zero amplitude in a periodic systema point at which the amplitude of one of the two kinds of displacement in a standing wave has maximum value
Term
 what is the range of frequency of hearing for humans?
Definition
 20-20,000 Hz
Term
 Draw a wave and label the graph: T, f, A, and λ
Definition
Term
 Define KE and PE
Definition
 energy due to an objects motionenergy due to an objects position
Term
 Can an object have KE and PE at the same time?
Definition
 YES--mid swing there is half and half
Term
 Can KE cancel? Can momentum cancel?
Definition
 No, there can never be a negative KEYes, it can cancel with momentum in the opposite direction
Term
 Why do golfers follow through and hit hard?
Definition
 To increase momentum, you can make change in momentum as large as possible if you increase force and increase time (i.e., swing through for a longer time and hit harder for greater force)
Term
 Compare and contrast energy and momentum
Definition
 Conservation of momentum is one of two cases--increase or decrease Conservation of energy--energy cannot be created or destroyed, only transformed. (Joule, 1850)however, momentum is the application of kinetic energy--the equation can be used to derive the Wnet equation.
Term
 A 1000-kg rocket has 40 million joules of KE. How fast is the rocket travelling?
Definition
Term
 Does a tree that falls in the woods make a sounds when it strikes the ground?
Definition
 Yes, because sounds is mechanical energy and when the tree falls it creates waves of vibration that are sound molecules.
Term
 why did the tacoma bridge of wa collapse in 1940?
Definition
 because of resonance, the strong winds blew that the same frequency of the bridge
Term
 Why does a punch hurt more with a bare hand than with a boxing glove on?
Definition
 Because the glove works to decrease momentum of the hand, it slows down the time it takes for the hand to reach the object, so the force is less
Term
 A book of mass 1-kg and with speed 200 cm/s has KE=?
Definition
Term
 GPE depends on...
Definition
 displacement (or height), mass, and acceleration due to gravity
Term
 KE depends on...
Definition
 mass and velocity(or moment of intertia and angular acceleration--for rotational KE)
Term
 Can KE be negative? PE?
Definition
 No and Yes, if it has a negative height (the refrence point is above the starting position and the object is travelling down)
Term
 how does one increase the momentum of a baseball?
Definition
 Increase force (throw harder) and increase time (follow through)
Term
 What is the speed of sound in air?
Definition
 344m/s
Term
 what happens to an object when Wnet is performed on the object?
Definition
 There is a change in the kinetic energy of that object.The forces on the object that are perpendicular do not change the KE, but those in the same or opposite direction of the motion do affect KE
Term
 Discuss the energy tranformations involved with a skier skiing down a steep hill
Definition
 First, the skier is stopped at the top of the hill and has GPE=mgh. Once the skier begins down the hill the GPE is somewhat transformed into KE=1/2mv^2. At the very bottom of the hill before it flattens out, the skier has GPE=0 and all KE. Once the skier reaches the flat part, he comes to rest and once again GPE=mgh, and KE=0.
Term
 Write down the three energy theorems.
Definition
 1. Wnet=ΔKE2. MEi=MEf (no friction)3. MElost=MEf-MEi (includes friction) [-fΔx=MEf-MEi]
Term
 Why do cars have "giveable" bumpers?
Definition
 To decrease momentum, if the bumper gives way, then it works to increase the time for a collision which decreases the force
Term
 What can work do?
Definition
 It can speed things up or slow things down
Term
 Define I and rotational variables
Definition
 Moment of inertia, resistance to an objects change in angular velocityconservation of angular momentum, if I gets smaller, ω (angular velocity) gets larger
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