11 Warm Up2) A block is pushed along a horizontal, frictionless surface, with a horizontal Force that varies as a function of time as shown in the graph here. The mass of the bloc is 3kg. If the block was at rest at time t=0, what is the speed of the block at time t=3?
13 Warm Up3) Three blocks of mass m, 2m, and 3m are placed adjacent to each other on a frictionless horizontal surface as shown above. A constant force of magnitude F is applied to the right. Which of the following statements is true?
15 Warm Up4) Two masses, M>m, are connected by a light string hanging over a pulley of negligible mass. When the masses are released from rest, the magnitude of the acceleration of the masses is?
16 Warm Up5) A mass of 2.0kg is attached to the end of a light cord to make a pendulum 5.0m in length. The mass is raised to an angle of 53 relative to the vertical, as shown, and released. The speed of the mass at the bottom of the swing is:
17 Warm Up6) A cannon is mounted on a cart, and carrying a cannonball. The total mass of the cart, cannon, and ball is M, and the cart is rolling with no friction at a velocity v in the positive direction as shown above. The ball, of mass m, is fired with a velocity vball in the positive x direction. What is the velocity of the cart and cannon after the ball is fired?
20 Warm Up a. X = 1/2 L b. X = 2/5 L c. X = 3/5 L d. X = 3/4 L 7) A student lies on a rigid platform of negligible mass, which is in turn placed upon two spring scales as shown above. The left scale at position 0 reads 200N, and the scale on the right at position L, reads 300N. Find the value of X in terms of L.a. X = 1/2 Lb. X = 2/5 Lc. X = 3/5 Ld. X = 3/4 Le. X = 4/5 LPIVOTPOINT
23 Warm Up9) A pendulum driven clock, located on earth, is set into motion by releasing its 10m long simple pendulum from a maximum angle of less than 10° relative to the vertical. At what approximate time t will the pendulum have fallen to a perfectly vertical orientation? (Use 10 for g)
25 a,b,c,d a,c,b,d d,b,c,a d,a,c,b Warm Up 10) By visual inspection, order the PV diagrams shown from the most negative work done on the system to the most positive work done on the system.a,b,c,da,c,b,dd,b,c,ad,a,c,b
27 AnnouncementsPass Back Fluids Quiz:Thermo Quiz Friday!
28 What are important quantities in thermodynamics? Pressure Atoms colliding w/ wall of a containerTemperature How fast atoms moveVolume How much space atoms “need” to move freelyNumber of molecules Really big numbers
29 Kinetic Theory of Gases Assumptions for an IDEAL GAS 1) Atom are bouncy:Elastic collisions between atoms2) Atoms are spread out:Far away unless colliding3) Atoms are random:No preferred direction of motion (means pressure is equal everywhere in a container
30 Calculation – Units to use Pressure ALWAYS Pascals (N/m2 )Temperature ALWAYS Kelvin (273 + oC)Volume ALWAYS m3 (Liters/1000)Number of molecules moles or moleculesMoles = Molecules/6.02E23R = 8.31J/molKKb = 1.38 E-23 J/K
31 Equation’s so far PV = nRT PV = NkbT P1 V1 / T1 = P2 V2 / T2 M is molar mass
32 GAS CONTRACTS (WORK ON) Energy of a GasΔU = Q + WU = 3/2 nRTU = 3/2 PVEnergy Type(+)(-)U = Internal energyTemp INCREASETEMP DECREASEQ = HEATHEAD ADDEDHEAT REMOVEDW = WorkGAS CONTRACTS (WORK ON)GAS EXPANDS (WORK BY)
33 Gas ProcessThe thermodynamic state of a gas is defined by pressure, volume, and temperature.A “gas process” describes how gas gets from one state to another state.
34 Isothermal Process (constant temperature) Hayon: Pull plunger up from halfway (slowly)T1PVDT = 0 (constant T)
35 Isobaric Process (constant pressure) Hayon: Heat up the tank while allowing plunger to moveIsobaric Process (constant pressure)PVIsobaric ExpansionIsobaric ContractionDP = 0 (constant P)
36 Isometric Process (constant volume) Hayon: Push to the top and then heat up or push to the bottom and then cool downPVNO WORK POSSIBLE!!DV = 0 (constant V)
37 Adiabatic process (PERFECTLY insulated) NO HEAT IS TRANSFEREDTisothermPVadiabatΔU = WQ = 0 (no heat enters or leaves)
38 U = 3/2 nRT Example Problem 0.25 moles of a gas are kept at 1150K. The gas undergoes adiabatic expansion, reaching a final temperature of 400K. How much work was done on or by the gas?U = 3/2 nRT
39 WORK = Area under a PV Diagram Using PV DiagramsHayon: Test (remember area) and don’t use 1 way valveWORK = Area under a PV DiagramPV(+) = Contract(-) = Expand200kpa100kpa250m2300m2
40 Free Response Problems FR #1 as an ExampleWeb Assign: Thermo Assignment #2Then skip #2 and go to the back