or...

incorrect cards (0)
correct cards (0)
remaining cards (0)
0:01

Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.

Normal Size     Small Size show me how

# THE MCAT PHYSICS-3

### WORK, ENERGY, MOMENTUM

What are the 3 types of potential energy? gravitational, elastic, electric
What does potential energy depend on? Difference between initial and final heights
Stiff springs have smaller / larger "k" value larger k
open system energy and mass are exchanged with surroundings
closed system energy is exchanged with surroundings but mass is not
isolated system neither energy or mass is exchanged with surroundings
Give examples of conservative forces. gravity, spring force, electromagnetic
Define conservative force -energy removed is same as energy recovered -force produces same amount of work regardless of path taken
What are 2 ways to see if it is a conservative force? 1.) Sum of work to move particle in a round trip = 0 2.) Sum of work needed to move a particle between two points is same regardless of path taken
Formula for conservative forces KE + PE = KE + PE
Work done against a conservative force is conserved in? Potential Energy
What kind of system is the universe? Isolated system
Examples of nonconservative force friction and air resistance
Define nonconservative force Energy removed cannot be recovered and is no longer available for kinetic energy
Is non-conservative force path-dependent? YES!
Does NC / C forces do work? When is mechanical energy conserved? -Conservative forces do no work -- ME conserved -Non-conservative forces do work -- ME not conserved
Work done against NC force is conserved as? nothing
Conservation of Energy Equation KE + PE + W = KE + PE + W
What does friction affect? KE only
What is work done on a system without friction? W = Fdcostheta
What is work done on a system with friction? Use Energy Conservation equation
Why does conservative force do no work? Neither energy nor mass is gained or lost by the system
What is mechanical energy? -energy possessed by an object due to its motion/ position -can either be KE or PE
What are kinetic frictional forces? Friction takes KE of a moving object and transfers it into mvmt of individual molecules on surface of objects in contact with each other
How to relate work and friction? W = -f (friction) * x
What are 2 types of energy transfer? work and heat
What is work? -energy is transferred from one system to another via a force -system --> surroundings and vice versa
What is heat by definition and in relation to KE? -energy transfer by natural flow from warm --> cold body -sum of all KE of molecules in an object
Is work the same as energy? NO! --> Work is done on object whenever force acts upon it to cause it to be displaced
What do frictional forces change? change internal and mechanical energy
Do perpendicular forces do work? NO
Does work depend on distance traveled? NO --> only displacement --> path independent
2 equations for power P = W/t (rate of doing work) P = Fvcostheta
What are the 2 ways for energy to escape a system? work and heat
If system is same temperature as surroundings, where does energy change come from? work
What does it mean to do more work? greater "a" , greater "v", greater KE, less time to achieve displacement
What is positive work? force and distance applied in same direction
What is negative work? force and distance applied in opposite directions
Positive work done on an object object gains energy
Positive work done by object object loses energy
negative work done on object object loses energy
negative work done by object object gains energy
How does work compare between sliding down a frictionless inclined plane and free fall from same height? SAME
Any object with velocity must have? momentum
What is momentum? measure of a moving object's tendency to continue along its present path
What are 2 important points about momentum? -initial and final momentum always conserved -vector: momentum is constant in direction and magnitude
How can you make it more difficult to change path of a moving object? increase velocity and mass
Conservation of momentum With no external forces like friction, total momentum before and after collisions are constant
Compare momentum and mechanical energy Momentum is ALWAYS conserved but mechanical energy is NOT ALWAYS conserved (i.e. KE)
Compare elastic and inelastic collisions -Elastic: energy and momentum conserved / no deform -Inelastic: energy not conserved / momentum conserved / deform
What is impulse? Impact force during collision to change object momentum --> change in momentum --> force of collision multiplied by duration of collision
Impulse equation Fdeltatime = change in momentum
Do objects always experience the same magnitude of impulse? YES when momentum is conserved
What happens when balls hit each other and lose speed? lose kinetic energy and thus have inelastic collision
What happens when you pull spring away from equilibrium position? 1.) Restoring force pulls to left --> object accelerates and builds momentum 2.) decelerates once it passes equil. position 3.) force now pulls in opposite direction
What is dampened harmonic motion? lose energy from friction -energy and amplitude diminish -frequence and period remain constant
What does loss in energy in dampened harmonic motion affect? KE and PE
Why does period stay constant in dampened harmonic motion? Over time, object will cover less distance, but because its doing it at a reduced average speed, time to complete cycle will remain constant
What happens when spring is pushed away from equil position? PE = max, KE = 0, a = max, v = 0
What happens when spring is at equil. position? PE = min, KE = max, a = 0, v = max
When is the tension for a pendulum the greatest? Bob points down
What force opposes tension in a pendulum? mgcostheta
What is tangent to the arc of a pendulum? mgsintheta
Potential energy for a pendulum PE = -mgL(1 - costheta)
What are extrinsic properties? depends on amount and quantity of material -mass and energy
What are intrinsic properties? does not depend on amount and quantity of material -density and pressure
A 15eV photon collides with a proton with ionization potential = 13.6 eV. Describe what happens in relation to conservation of energy. 15eV photon first provides I.E. to unbind electron --> any excess energy becomes electron's KE
Work done by gravity is + / - when it moves down hill and +/- when it moves uphill. positive and negative
Going from PE --> KE, what does object gain? velocity --> gains momentum
Relate frequency and period. f = 1 / T
For work, in what direction must the force be directed? MUST BE PARALLEL TO MOTION
Where must the applied force be directed to change an object's KE? directed in direction of displacement
Does PE depend on the path taken? NO --> only difference btwn initial and final heights
How does work differ in terms of cos/sin between work done on object on ground and one on inclined plane? -ground = cos -inclined plane = sin
Why do lighter objects experience greater changes in velocity than heavier objects upon collisions? -Impulse equation: Ft = change in momentum -same impulse -->greater change in velocity
Impulse = momentum
Whether a car comes to rest abruptly or extended over time, how does momentum change? same change in overall momentum in both
When velocity of two objects after a collision decreases, is collision elastic or inelastic? inelastic --> lose speed and KE
Drop a ball and bounces up to same height - what type of collision? perfectly elastic collision
throw a ball at wall and it bounces back with same speed - what type of collision? perfectly elastic collision
Torque t = r*Fsintheta
In torque, what is the optimal positioning for radius and force? perpendicular!!
Trick to solving torque -indicate direction force is applied -radius is always perpendicular
Mechanical advantage M.A. = weight / applied force needed to support object
Objects with momentum always have...? KINETIC ENERGY
In a collision, what causes a change in momentum? impulse
does impulse = momentum? NO --> IMPULSE = MOMENTUM CHANGE
Created by: 507935299 on 2012-06-10