# Search results

1. ### Relativistic Time for spaceship movement

1. Homework Statement A certain star is 76.6 light-years away. How many years would it take a spacecraft traveling 0.946c to reach that star from Earth, as measured by observers on Earth? How many years would it take to reach that star from Earth, as measured by observers on the spacecraft...
2. ### Infared WAvelengths in transition through energy levels

1. Homework Statement How many transitions involving the hydrogen energy levels shown correspond to photons of infrared light? The infrared range is less than 1.8 eV 2. Homework Equations Paschen Lines = Infared wavelengths 3. The Attempt at a Solution I thought that since...
3. ### Destructive Interference when walking toward an antenna

1. Homework Statement Two antennas located at points A and B are broadcasting radio waves of frequency 96.0 MHz, perfectly in phase with each other. The two antennas are separated by a distance d=12.40m. An observer, P, is located on the x axis, a distance x=55.0m from antenna A, so that APB...
4. ### Phase Difference between two waves from antennas

1. Homework Statement Two antennas located at points A and B are broadcasting radio waves of frequency 96.0 MHz, perfectly in phase with each other. The two antennas are separated by a distance d=12.40m. An observer, P, is located on the x axis, a distance x=55.0m from antenna A, so that APB...
5. ### Pathlength Difference from two waves

1. Homework Statement Two slits separated by a distance of d = 0.12mm are located at a distance of D = 780mm from a screen. The screen is oriented parallel to the plane of the slits. The slits are illuminated by a coherent light source with a wavelength of lambda = 549E-6 mm. The interference...
6. ### Speed of a 796eV electron

1. Homework Statement What is the speed of a 796eV electron? 2. Homework Equations E = hc/lambda E = hv 3. The Attempt at a Solution I'm not sure how to get a value for meters... I know if I take h (plank's constant) and divide the electron, I will get 4.14E-15 ev*s / 796 eV =...
7. ### Real Object, Images formed by a single converging or diverging lens

1. Homework Statement Starting with a real object, which of the following statements are TRUE about the image formed by a single lens? (Choose ALL correct answers, e.g. B, AC, CDF.) A) For a converging lens an object has to be placed between the focal length and the lens in order to form a...
8. ### Angle of Incidence with partial reflection and partial refraction

1. Homework Statement A beam of light in air strikes a piece of glass (n=1.51) and is partially reflected and partially refracted. Find the angle of incidence if the angle of reflection is twice the angle of refraction. 2. Homework Equations n1sintheta1 = n2sintheta2 3. The...
9. ### Solving for a variable when the square root of a formula is in the denominator

1. Homework Statement solve for x: [ x / sqrt(x^2 + h^2) ] = [ d / sqrt(d^2 + h^2) ] I need to solve for x. 2. Homework Equations sq rt * sq rt = what is inside the square root square both sides of an equation 3. The Attempt at a Solution Can anyone help me remember...
10. ### Index of Refraction and actual location of fish in water

1. Homework Statement After finishing your physics classes with the firm conviction that the questions were strange and out of touch with reality, you decide to take up spear fishing. While wading through water (of index of refraction=n and depth h) you spot a fish that appears to be a...
11. ### Electric Field of an EM wave

1. Homework Statement A 1.10m long FM antenna is oriented parallel to the electric field of an EM wave. How large must the electric field be to produce a 1.28 mV voltage between the ends of the antenna? 2. Homework Equations u = EoErms^2 I = uc Intensity = Power / area 3. The...
12. ### Laser Beam and index of refraction

1. Homework Statement A laser beam enters a 10.0cm thick glass window at an angle of 30 degrees from the normal. The index of refraction of the glass is 1.46. At what angle from the normal does the beam travel through the glass? 2. Homework Equations sin theta 1 / sin theta 2 = n1 / n2...
13. ### Supernova energy reached by detector disk 1560 light years away

1. Homework Statement A super nova releases 1.9E45 J of energy over a 10 day period. It is 1560 ly from earth. A detector, facing the star, is a disk of radius 7cm. How much energy reaches the detector? (The detector is in orbit, so it can face the star for the entire 10-day period) 2...
14. ### Induced Current - is there one if inside constant B field?

1. Homework Statement A box of wire is moving within a constant B field. Is there an induced current? 2. Homework Equations Slap rule 3. The Attempt at a Solution Since the wire is experiencing constant B field, how would we figure out whether or not there is a current? I know...
15. ### Parallel conducting wires and zero magnetic field x value

1. Homework Statement Consider two parallel conducting wires along the direction of the z axis as shown below. Wire 1 crosses the x-axis at x = -1.10cm and carries a current of 3.50A out of the xy-plane of the page. Wire 2 (right) crosses the x axis at x = 1.10cm and carries a current of 6.20A...
16. ### Electric Field between two metal plates

1. Homework Statement Two square metal plates are placed parallel to each other, separated by a distance d= 2.34 cm. The plates have sides of length L= 0.750 m. One of the plates has charge Q=+ 2.70 x10-3 Coulombs, while the other plate has charge -Q. What is the magnitude of the electric...
17. ### Magnitude and direction of induced current with magnetic field

1. Homework Statement A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance of 8 ohm. The wire and rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied out of the paper. An applied force moves the rod to the...
18. ### Direction of Magnetic Field when given velocity and force

1. Homework Statement An electron, moving west, enters a magnetic field of a certain strength. Because of this field the electron curves upward. What is the direction of the magnetic field? 2. Homework Equations Right Hand Rule 3. The Attempt at a Solution I don't understand what...
19. ### Radius of a circle with a magnetic field and electron velocity

1. Homework Statement An electron moving perpendicular to a magnetic field of 2.2*10^-2 T moves in a circle of certain radius. If the electron is moving with a speed of 1.5*10^7 m/s, what is the radius of the circle? 2. Homework Equations B field = u0*I / 2 pi r F = qvB 3. The...
20. ### Four Wires and y component of magnetic field at center

1. Homework Statement The four wires that lie at the corners of a square of side a=5.10cm are carrying equal currents i=2.40Amps into (+) or out of (-) the page, as shown in the picture. Calculate the y component of the magnetic field at the center of the square. 2. Homework Equations...
21. ### Behavior of a circuit when values increase or decrease

1. Homework Statement Consider the behavior of the circuit, when various values increase or decrease. (Select I-increases, D-decreases, If the first is I and the rest D, enter IDDDDD). A) If R3 decreases, the current through R4 ___. B) If R3 decreases, the current from the battery ___...
22. ### Magnitude of Electric field using superposition principle

1. Homework Statement Two charges, +q and -q, are located in the x-y plane at points (0,+d/2) and (0,-d/2), respectively. Calculate the magnitude of the electric field at point P with the superposition principle. Data: q=37.0 nanoCoulombs, d=4.60mm and P at x=92.0mm. 2. Homework...
23. ### Current through 6 resistors in series and parallel

1. Homework Statement See attached figure. All resistors have the same resistance of 2.00kilo-Ohm. Assume V = 12V. Calculate the current through resistor R6 and resistor R5. 2. Homework Equations V = IR I = V/R R total (series) = R1 + R2.....etc 1/R total (parallel) = 1/R1 +...
24. ### Power, Voltage and Current - Hairdryer Problem

1. Homework Statement A typical household circuit is capable of carrying 30.0 A of current at 120 V before the circuit breaker will trip. How many 1500-W hair dryers can run off one such circuit? Use the relation between power, current and voltage. Also, remember hair dryers come in integer...
25. ### Short in Wires with 2 Different Resistances

1. Homework Statement An underground telephone cable, consisting of a pair of wires, has suffered a short somewhere along its length (at point P in the Figure). The telephone cable is 6.00 km long, and in order to determine where the short is, a techician first measures the resistance between...
26. ### Electrical Potential Energy Converted to Kinetic Energy

1. Homework Statement The potential difference between two parallel conducting plates in vacuum is 330 V. An alpha particle with mass of 6.50 x10-27 kg and charge of 3.20 x10-19 C is released from rest near the positive plate. What is the kinetic energy of the alpha particle when it reaches...
27. ### Calculating Force at an angle with kinetic friction coefficient

1. Homework Statement A force, F, applied to a 12.1 kg crate at an angle (theta) of 41.0 degrees makes the crate move horizontally with a constant acceleration of 1.85 m/s^2. The coefficient of kinetic friction between the crate and the surface is uk=0.35. Calculate the magnitude of F...
28. ### Finding an electric field magnitude with tension and weight of hanging ball

1. Homework Statement As shown in the figure above, a ball of mass 0.720 g and positive charge q =39.4microC is suspended on a string of negligible mass in a uniform electric field. We observe that the ball hangs at an angle of theta=15.0o from the vertical. What is the magnitude of the...
29. ### Finding potential of two points in a constant electric field

1. Homework Statement The figure below shows two points in an E-field: Point 1: (3,4) and Point 2: (12,9) both in m. The electric field is constant, with a magnitude of 80 V/m, and is directed parallel to the +X axis. The potential at point 1 is 1100 V. What is the potential at point 2...