3. Geodesics in R² : Consider 2D flat space in polar coordinates r and θ. Find the curves parametrized by r(s) and θ(s) that satisfy the geodesic equation, and show that they correspond to straight lines in R²

Friction lab Analysis: 1. HOW I CAN Construct a graph of friction vs Normal force. Can I plot both Static and Kinetic friction on a single Excel Graph and how. 2. How can I use this graph to find the coefficient of static and kinetic friction? (Hint: Think about how we found mass in the Newton’s second law experiment)

An 8.00-cm-long piece of wire is formed into a square, and carries a clockwise current of 0.150 A. The loop is placed inside a solenoid, and the plane of the loop is perpendicular to the solenoid’s magnetic field. The solenoid carries a counterclockwise current of 17.0 A, and has 25 turns per centimeter. What is the force on each side of the loop?

Please explain

Compare the passage of charged and uncharged particles through matter. What are the approximate probabilities of a single charged particle achieving a path- length equal to twice its range, or of a single photon having a pathlength twice as great as the mean free path lip? (Assume the photon is totally absorbed in its first interaction.)

Its a video of a glider pushed forward and going back due to a fan blowing of the opposite direction of being pushed.

After watching this video, Blake, a student in an introductory physics class, makes the following claim:

The acceleration and velocity of the glider are both momentarily zero when the glider changes direction. The velocity of the glider must be zero for an instant when the glider changes direction. Because the velocity is zero, the acceleration must also be zero.

Respond to Blake's claim. Which parts, if any do you agree with, and which parts do you not agree with? To support your response, use evidence from your experience, or from the videos in this activity.

A series circuit contains a 3.00 H inductor, a 3.00

A γ-ray which has energy of 400 keV collides with an atom and undergoes Compton scattering.

(a) What is the energy of the wave in Joules and hence what is its frequency?

(b) If the change in the angle of the γ-ray is 20°, what is the frequency of the wave as it exits the atom?

In Aluminium, the attenuation of a γ-ray is described by the attenuation coefficient μ=0.25 cm-1. What are the values for the following:

(c) The relaxation length

(d) The half value thickness

(e)The amount of attenuation of 3 cm of Aluminium, assuming the buildup factor is 1.

1. Look up “heat engines” on the Internet. There will be a lot of technical discussion meant for engineers. Can you find any novel heat engines? Look up “nitinol engine.” Can you find heat engines that claim to work on small temperature differences? Do they discuss the poor efficiency that you get with small temperature differences (from the efficiency equation)?

1. The formula ∆? = ???∆? is only good if ∆? is not too large. According to your textbook, what is considered a “not too large ∆??” (a) ∆? ≈ 1 ?° or less (c) ∆? < 100 ?° or so (b) ∆? ≈ 10 ?° or less (d) ∆? < 200 ?° or so

2. In the formula ∆? = ???∆?, what is ?? (a) The specific heat of the substance (b) The thermal resistivity of the substance (c) The latent heat of fusion of the substance (d) The coefficient of thermal expansion of the substance (e) One-third of the coefficient of linear thermal expansion of the substance.

3. Find this passage in section 17.4 and fill in the blank. This is an important statement: For ___________ materials we can find a simple relationship between the volume expansion coefficient  and the linear expansion coefficient  . (a) most (d) frozen (b) all (e) liquid (c) solid

4. What is that simple relationship between ? and ?? (a) ? = 3? (d) ? = 1 3 ? (b) ? = 2? (e) ? = 3 2 ? (c) ? = 1 2 ? 5. The table of coefficients of expansion in the textbook lists ? for glycerin as 49 × 10−5 K−1. Would it be correct, then, to say that ? for glycerin must be about 16.3 × 10−5 K−1 (a) Sure, if ∆? is not too large, as specified before. (b) No, we cannot specify ? for a substance like glycerin.

6. Which of the following is the most reasonable problem-solving approach? (a) We can always use ∆? = ???∆? when dealing with solids; but we use ∆? = ?? ?∆? when dealing with gases or liquids. (b) We can always use ∆? = ???∆? and cube the result if we want ∆?. (c) Apply ∆? = ???∆? to the longest dimension of an object only. (d) We can use ∆? = ???∆? only for metals; for all other substances use ∆? = ?? ?∆?.

7. Two cylinders made of the same material and have the same external dimensions, but one is solid and the other is hollow. Their temperature is increased to the same final temperature and they expand. How will their final sizes compare? (a) They will still have the same external dimensions. (b) The hollow one will be larger. (c) The solid one will be larger.

8. Why is it sometimes possible to loosen metal caps on screw-top glass jars by dipping the capped jar briefly into hot water? (a) The hot water makes the cap expand, but not the bottle. (b) The hot water makes the bottle contract while the cap expands. (c) The metal cap expands more than the glass bottle for the same T.

9. Go to Page 547 and look at Figure 17.3 that shows a bimetallic strip. A bimetallic strip is made by bonding two different materials that have the same dimensions at the same initial common temperature. Suppose that in Figure 17.3 metal 1 is copper. Which of the following materials could be used for metal 2? (a) Steel (b) Invar (nickel-iron alloy) (c) Brass

10. The figure shows a rectangular brass plate at 0°C in which there is cut a rectangular hole of dimensions indicated. If the temperature of the plate is raised to 150°C: (a) x will increase and y will decrease (b) both x and ywill decrease (c) x will decrease and y will increase (d) both x and ywill increase (e) the changes in x and y depend on z

11. When water at 2°C absorbs heat, what happens? (a) It melts while its volume increases. (b) It warms up while its volume increases. (c) It cools down while its volume decreases. (d) It vaporizes as it cools down. (e) It warms up while its volume decreases.

12. The coefficient of linear expansion of steel is 12 x 10–6 /C°. A railroad track is made of individual rails of steel 1.0 km in length. By what length would these rails change between a cold day when the temperature is –10°C and a hot day at 30°C? (a) 0.62 cm (d) 480 cm (b) 24 cm (e) 620 cm (c) 48 cm

13. A steel tank of volume 0.0700 m3 is filled to the top with gasoline at 20.0°C. The tank is placed inside a chamber at a temperature of 50.0°C. The coefficient of volume expansion for gasoline is 9.50 x 10–4 /C°; and the coefficient of linear expansion of steel is 12.0 x 10–6 /C°. After the tank and its contents reach thermal equilibrium with the chamber, how much gasoline has spilled? (a) 2.52 x 10–5 m3 (b) 7.56 x 10–5 m3 (c) 1.69 x 10–3 m3 (d) 1.92 x 10–3 m3 (e) 3.00 x 10–3 m3   

14. A copper plate has a length of 0.12 m and a width of 0.10 m at 25°C. The plate is uniformly heated to 175°C. If the linear expansion coefficient for copper is 1.7 x 10–5 /C°, what is the change in area of the plate as a result of the increase in temperature? (a) 2.6 x 10–5 m2 (b) 6.1 x 10–5 m2 (c) 3.2 x 10–5 m2 (d) 4.9 x 10–5 m2 (e) 7.8 x 10–5 m2

15. A ring made of steel has a 2.5000-in inside diameter when the temperature is 20.0°C. The ring will be warmed until it can fit around a brass rod of 2.5020-in outer diameter. Calculate to what temperature should the ring be warmed. (a) 83.4 °C (b) 86.7 °C (c) 82.1 °C (d) 833 °C (e) 66.6 °C  

16. During heat conduction, the heat transfer (“heat flow”) is always (a) From higher to lower temperature (b) From lower to higher temperature (c) Could be either way, depending on the type of material

17. According to the textbook, why are many insulating materials such as Styrofoam and fiberglass good insulators? (a) Because they are always colder than the environment. (b) Because they tend to have low specific heats. (c) Because they contain mostly dead air. (d) Because they cannot be heated. (e) Because their melting points are very high.

18. Which of the three modes of heat transfer is the one that depends on moving matter from one region to another? (a) Conduction only. (d) Both conduction and convection. (b) Convection only. (e) None of them – heat is not matter. (c) Radiation only.

19. You will use fiberglass to insulate a house. If a space 6 inches wide (that’s 15.24 cm) is to be completely filled with fiberglass, what will be the thermal resistance of the fiberglass layer? (a) 0.0061 m2·K/W (d) 3.81 m2·K/W (b) 0.260 m2·K/W (e) 150 m2·K/W (c) 2.23 m2·K/W

20. You need to come up with a layer of material that provides a thermal resistance of 20 W/m·K. Which of the following will give you that resistance with the thinnest layer? (a) Brick, red (d) Glass (b) Styrofoam (e) Felt
21. This diagram shows four slabs of different materials with equal thickness, placed side by side. The temperatures at the interfaces are shown. Assume heat conduction is happening at a steady rate. Rank the materials according to their thermal conductivities, lowest to highest. (a) 3, 4, 2, 1 (b) 4, 3, 2, 1 (c) 1, 2, 3, 4 (d) 2, 1, 3, 4 (e) 3, 4, 1, 2   

22. At what rate is heat lost through a 1.0m x 1.5m rectangular glass window that is 0.5 cm thick when the inside temperature is 20°C and the outside temperature is 5°C? (a) 18 W (d) 3600 W (b) 36 W (e) 7200 W (c) 720 W

23. A granite wall has a thickness of 0.61 m and a thermal conductivity of 2.1 W/m·K. The temperature on one face of the wall is 3.2 °C. The other face is at 20.0°C. How much heat is transferred in one hour through each square meter of the granite wall? (a) 2.1 x 105 J (d) 1800 J (b) 1.1 x 105 J (e) 58 J (c) 7.7 x 104 J

Questions 24, 25 and 26 are about the following situation: A cooking pan placed on a stove has a copper bottom that is 8.50 mm thick and 0.150 m2 in area. The water inside the pan is at 100.0°C and 0.390 kg are being evaporated every 3.00 min.

24. How much heat energy is needed to evaporate each 0.390 kg of water? (a) 8.80 x 105 J (b) 1.30 x 105 J (c) 1.63 x 105 J (d) 7.52 x 105 J

25. At what rate is the heat being supplied by the stove? (a) 2.93 x 105 W (b) 7.22 x 102 W (c) 9.06 x 102 W (d) 4.89 x 103 W

26. What is the temperature of the bottom surface of the pan (the surface in contact with the stove)? (a) 143.13°C (b) 100.72 °C (c) 100.11 °C (d) 118.24 °C

27. A 150-W filament lightbulb is operating at a temperature of 2450 K. The emissivity of the surface of the filament material is 0.350. Assuming all the 150-W are radiative power, calculate the surface area of the filament. (a) 2.1 x 10-4 m2 (b) 3.1 x 10-6 m2 (c) 4.4 x 10-4 m2 (d) 7.4 x 10-5 m2 Questions 28 and 29 are about the following situation: The surface area of your body is approximately 1.71 m2. The emissivity of dry skin is approximately 0.891. The normal skin-surface temperature is 33.3 °C.

Assume you are in a room where the temperature is a constant 20.0 °C. 28. What is the radiation current your skin receives from the room environment? (a) 2.53 x 10-5 W (b) 1.38 x 10-2 W (c) 66.8 W (d) 638.0 W (e) 1256 W

29. What is the net radiation power of your skin? Is it a net input or a net output? (a) 0.0924 W, a net output (b) 0.106 W, a net input (c) 2.70 x 10-3, a net output (d) 123.9 W, a net output (e) 638.0 W, a net input



30. What is the power output of radiation of this person’s body? (Just the output, not the net.) (a) 0.0024 W (d) 815 W (b) 0.092 W (e) 958 W (c) 143 W 31. What is the power of radiation absorption from the surroundings for this person? (a) 0.0024 W (d) 815 W (b) 0.012 W (e) 958 W (c) 143 W 32. The net radiation power is only about 80% of the basal metabolic rate. What is the basal metabolic rate of this person? (a) 179 W (d) 0.00294 W (b) 114 W (e) 0.099 W (c) 1019 W   

if you toss a ball in projectile motion but used two balls of masses 20 and 30 grams, how would mass affect their motions in the X and Y direction? Please explain in detail.

A line of charge (with charge per unit length given by λ) extends from (0,0,0) along the x axis to infinity. Answer the following 2 questions about the electric field at the point (x,y,z) = (0,a,0).

1. A correct integral expression for the y component of the electric field at this point is given by which of the following? In each case the integral has limits 0 and ∞.
   1. λ/(4πε₀)∫dx a/(a² + x²)^3/2 k
   2. λ/(4πε₀)∫dx a/(a² + x²)^3/2 j
   3. λ/(4πε₀)∫dx a/(a² + x²)     j
   4. λ/(4πε₀)∫dx a/(a² + x²)^1/2k
   5. none of a-d   

2. What is the y component of the electric field at this point? Hint: remember (or calculate using Gauss’s law) the electric field a distance a from an infinite wire and think of a symmetry argument that allows you to answer the question without a more complicated calculation.

1. E_y = λ/(4πaε₀) j
2. E_y = λ/(2πaε₀) j
3. E_y = λ/(4πaε₀) k
4. E_y = λ/(2πaε₀) i    
5. none of a-d                                                                             

3. Which of the following is(are) true about a charged particle in a uniform, static (time-independent) magnetic field?
   1. The magnitude of the magnetic force on the particle depends only on the charge, the magnetic field and physical constants.
   2. The magnitude of the magnetic force on the particle depends on the direction of motion of the particle
   3. The work done on the particle by the magnetic force depends on the velocity of the particle.
   4. If the particle is moving, the magnetic force on the particle cannot be zero.
   5. More than one of a-d

4. The centers of the moon and the Earth are separated by 3.84 x 108 m. The moon has a mass of 7.34 x 1022 kg. The mass of the earth is 5.97 x 1024 kg.

Given:

a. Find the gravitational attraction between the earth and moon.

b. Find the acceleration of the moon toward the earth.

c. Find the speed of the moon in its orbit.

d. Find the circumference of the orbit.

e. Calculate the time it takes the moon to travel around the earth in days.

The magnetic field of a uniform plane wave that propagates in a vacuum, is given by the expression:

B (r, t) = (10^−6 )[xˆ + 2yˆ + Bzzˆ] cos [ωt + 3x - y - z] in m.k.s.units and where xˆ, yˆ, zˆ are unit vectors along the cartesians axes . Find:

(a) The propagation direction.

(b) The wavelength λ.

(c) The angular frequency ω.

(d) The associated electrical field