Final: Tuesday, April 29, 7pm, 202 Brooks Makeup Monday April 28, 1pm, 437 White Hall

Transcription

1 Final: Tuesday, April 9, 7pm, 0 Brooks Makeup Monday April 8, 1pm, 437 White Hall 67% focused on this last section of the course Chapters , 11.1-, , 13(all), , 5.4 There will also be problems from Chapters 1-7 (motion, forces, energy, momentum, rotation) Totaling 5 multiple choice questions

2 You should be able to convert between K/C/F temperature scales Fahrenheit to Celsius T F = T C x (9/5) + 3 T C = (T F -3) x (5/9) Kelvin to Celsius T K = T C T C = T K Not a simple factor conversion T C = T F *5/9 T C = T K For more problems on Ch. 10 & 11, see lectures and following problem solving day

3 You should be able to calculate the amount of thermal expansion Length expansion (thermometer) L=αL o T Area expansion (ring) A=γA o T Volume expansion (basketball) V=βV T Note: T is in C (or K) Note: γ=α, β= 3α Thermometers rely on a thermal expansion of a liquid (e.g. mercury)

4 Main Ideas in Chapter 11 You should be able to: Understand the ways to transfer heat (mostly conceptually except conduction) Calculate heat necessarily to raise the temperature or change the phase of a material Extra Practice: 11.1, 11.3, 11.5, 11.7, 11.9, 11.15, 11.17, 11.5, 11.7, 11.33

5 Phase changes (e.g. solid to liquid) When heating ice into water and then into steam the temperature does not go up uniformly Different slopes since c water > c ice Flat bits at phase changes Q = m c T c called the specific heat of a material c water = 4190 J/(kg K) - difficult to heat c ice = 090 J/(kg K) Temperature Boiling Point ice ml f water steam ml v Melting Point Time L f <L v Applying constant heat per second

6 3 mechanisms Conduction Transferring heat energy Heat transfer through material (rods, windows, etc.) Convection Heat transfer by movement of hot material (hot air, hot liquid while cooking) Radiation Heat transfer by light (sun, fire, tanning bed)

7 Rate of heat flow (Conduction) L Energy flows from higher temp. to lower temp. (0 th law) Rate of energy transfer (P=power) depends on Temperature difference (T H -T C ) Area of contact (A) and length (L) over which heat flows Thermal conductivity of the material (k) k (copper) = 385 W/(m K) good conductor k (air) =0.0 W/(m K) good insulator Higher k means more heat flow - P in Watts, Q in Joules, t in seconds P = Q t T = ka T L H C L

8 Main Ideas in Chapter 13 You should be able to: Understand Simple Harmonic Motion (SHM) Determine the Position, Velocity and Acceleration over time Find the Period and Frequency of SHM Relate Circular Motion to SHM Extra Practice: C13.1, C13.3, C13.11, 13.1, 13.3, 13.5, 13.9, 13.11, 13.17, 13.19, 13.1, 13.3, 13.5, 13.7, 13.31

9 Period and Frequency Independent of Amplitude Period of a spring The period (T) of a mass on a spring is dependent upon the mass m and the spring constant k Frequency T = π ƒ = m k The frequency, ƒ, is the number of complete cycles or vibrations per second; units are s -1 or Hertz (Hz) The angular velocity is related to the frequency ω = πƒ = The angular velocity/speed (or angular frequency) gives the number of radians per second 1 T k m

10 Graphical Representation of Motion When x is a maximumor minimum, velocity is zero When x is zero, the speed is a maximum (slope of x) Acceleration vs. time is the slope the of velocity graph. When x is max in the positive direction, a is max in the negative direction

11 Velocity as a Function of Position Conservation of Energy allows a calculation of the velocity of the object at any position in its motion v k = ± m Speed is a maximum at x = 0 Speed is zero at x = ±A 1 mv + kx = ka 1 ( A x ) The ±indicates the object can be traveling in either direction 1 1 mv v max max = = 1 k m ka A

12 More Ideas in Chapter 13 You should be able to: Understand the pendulum Determine different kinds of waves Find the wavelength, frequency and speed of a wave Damped Oscillations

13 F The Simple Pendulum = mg L Since restoring force is proportional to negative of displacement, pendulum bob undergoes SHM. Effective spring constant is k eff =mg/l x T = π spring m k eff T = π pendulum L g

14 Pendulum If a pendulum clock keeps perfect time at the base of a mountain, will it also keep perfect time when it is moved to the top of the mountain? If not, will it run faster or slower? No, g is slightly smaller at higher altitude. T = π L g T will be bigger so it will take longer to complete an oscillation.

15 Types of Waves traveling wave Transverse v = λf Longitudinal

16 Are you on the right wavelength? If the wave below has a velocity of 6 m/s, answer the following: What is the wavelength? m What is the wave s period? What is the wave s frequency? T= λ/v = m/(6 m/s) = s f =1/T = 1/0.333s = 3 Hz v = λ = T λ f 6 m/s m

17 Main Ideas in Chapter 14 You should be able to: Explain how a vibrating object affects the nearby air molecules to produce sound waves Calculate the speed, intensity and decibelsof sound

18 Determining distance with echoes A man shouts and hears his echo off a mountain 5 seconds later. How far away is the mountain? Speed of sound ~343m/s at room temperature Compare to thunder

19 One of the loudest sounds on Earth was made by the volcanic eruption of Krakatoain Indonesia in August of At a distance of 161 km, the sound had a decibel level of 180 db. How far away from the source would you be to not experience pain (<10 db).

20 A 1 kg block slides 3 m from rest down a frictionless ramp with an incline angle of 35 before being temporarily stopped by a spring with spring constant k=30,000 N/m. By how much is the spring compressed when the block stops? How should we approach this problem? D = 3m m= 1 kg θ= 35

21 A spring with spring constant 300 N/m is attached to an object whose mass is.0 kg. If the spring is initially stretched A=0.5 m, what is the velocity of the object at x = 0, -A and A/? 1 mv + kx = ka 1 1 v k = ± m ( A x )