# Search results

1. ### Magnitude of Magnetic Field

Homework Statement A rectangular loop of wire is moving toward the bottom of the page with a speed of .042 m/s. The loop is leaving a region in which a magnetic field is directed into the page; the magnetic field outside this region is zero. If during the time of 1.5 s the magnitude of the...
2. ### Energy homework problem help

Homework Statement The atomic mass of gold-197 is 196.96654 u. How much energy is required to completely separate the nucleons in a gold-197 nucleus? Homework Equations E = 196.96654 u x 931.5 The Attempt at a Solution I did the above calculation and got 1.83e5 MeV but im pretty...
3. ### Proton distance help

Homework Statement A proton is released from rest at t=o in a uniform electric field whose magnitude is 2.5e-8 N/C. How far has the proton traveled after .5 s? Homework Equations x = vot + 1/2at^2 The Attempt at a Solution x = 1/2(9.81)(.5)^2 = 1.2 but it says the answer is...
4. ### Lens Power (diopters)

Homework Statement A middle-aged man starts to wear eyeglasses with lenses of 2.0 D that allow him to read a book held as close as 25 cm. Several years later, he finds that he must hold a book no closer than 35 cm to read it clearly with the same glasses, so he gets new glasses. What is the...
5. ### Images on a retina

Homework Statement Which forms the larger image on the retina of your eye: a 43 ft tree seen from a distance of 210 ft, or a 12 in flower viewed from a distance of 2.0 ft? Homework Equations none? The Attempt at a Solution I don't really understand how you would go about working...
6. ### Image Height

Homework Statement Your friend is 1.7 m tall. What is the height of her image when she is 4.2 m from you? Homework Equations I used di/do and multiplied that by the height of the friend The Attempt at a Solution I did (4.2/3.5)(1.7) but it was wrong. Not really sure what I'm...
7. ### Focal length / Object height

Homework Statement An object is located 27.5 cm from a certain lens. The lens forms a real image that is twice as high as the object. b) Now replace the lens used in Part A with another lens. The new lens is a diverging lens whose focal points are at the same distance from the lens as the...
8. ### Index of Refraction

Homework Statement While studying physics at the library late one night, you notice the image of the desk lamp reflected from the varnished tabletop. When you turn your Polaroid sunglasses sideways, the reflected image disappears. If this occurs when the angle between the incident and...
9. ### Light Refraction

Homework Statement A kitchen has twin side-by-side sinks. One sink is filled with water, the other is empty. 1) Does the sink with water appear to be deeper, shallower, or the same depth as the empty sink? 2) Choose the best explanation from among the following: a) The sink with...
10. ### Convex Mirror / Virtual Image

Homework Statement The virtual image produced by a convex mirror is one-quarter the size of the object. b) What is the focal length of this mirror? Homework Equations 1/di = 1/f - 1/do The Attempt at a Solution i found di to be -9.3 cm but when i solved for f i keep getting it...
11. ### Magnification/Focal Length

Homework Statement Shaving/makeup mirrors typically have one flat and one concave (magnifying) surface. You find that you can project a magnified image of a lightbulb onto the wall of your bathroom if you hold the mirror 2.0 m from the bulb and 3.7 m from the wall. a) What is the...
12. ### Plane Mirrors

Homework Statement You are 1.9 m tall and stand 3.5 m from a plane mirror that extends vertically upward from the floor. On the floor 1.5 m in front of the mirror is a small table, 0.80 m high. a) What is the minimum height the mirror must have for you to be able to see the top of the...
13. ### Calculating current

Homework Statement You want to make a solenoid that is 38 cm long with 4300 turns. How much current should you run through the solenoid to produce a magnetic field of .75 T? Homework Equations B = uoNI The Attempt at a Solution I converted 38 cm to m (not sure where to use this...
14. ### Concave Mirrors

Homework Statement 1)A concave mirror produces a virtual image that is three times as tall as the object. a) If the object is 21 {\rm cm} in front of the mirror, what is the image distance? b) What is the focal length of this mirror? Homework Equations hi/ho di/do 1/f= 1/do...
15. ### Frequence of light of galaxy receding from earth

Homework Statement Most of the galaxies in the universe are observed to be moving away from Earth. Suppose a particular galaxy emits orange light with a frequency of 5e14 Hz. 1) If the galaxy is receding from Earth with a speed of 3325 km/s, what is the frequency of the light when it...
16. ### Mutual Inductance in a solenoid

Homework Statement A long solenoid (black coil) with cross-sectional area A cm^2 and length L is wound with n1 turns of wire. A time-varying current i1 flows through this wire. A shorter coil (blue coil) with n2 turns of wire surrounds it. Use (uo)(m*kg/s^2*A^2) 1) Find the value M of the...
17. ### Determine inductance of a solenoid

Homework Statement Determine the inductance of a solenoid with 650 turns in a length of 21 cm. The circular cross section of the solenoid has a radius of 4.2 cm. Homework Equations ??? The Attempt at a Solution I've looked all over my textbook and cant come up with a possible...
18. ### Turns of a Wire

Homework Statement A generator is designed to produce a maximum emf of 180 V while rotating with an angular speed of 3900 rpm. Each coil of the generator has an area of 2.0×10−2 m^2. a) If the magnetic field used in the generator has a magnitude of 4.1×10−2 T, how many turns of wire are...
19. ### Average induced EMF

Homework Statement The area of a 100 turn coil oriented with its plane perpendicular to a 0.28 T magnetic field is 4.3×10−2 m^2. Find the average induced emf in this coil if the magnetic field reverses its direction in 0.36 s. Homework Equations E = -N (flux - flux initial)/(t-to)...
20. ### Magnetic Field Direction

Homework Statement A 0.49 m copper rod with a mass of 0.13 kg carries a current of 10 A in the positive x direction. Let upward be the positive y direction. 1) What is the magnitude of the minimum magnetic field needed to levitate the rod? 2) What is the direction of the minimum magnetic field...
21. ### Loop current / torque

Homework Statement A rectangular loop of 260 turns is 33 cm wide and 17 cm high. What is the current in this loop if the maximum torque in a field of 0.49 T is 24 N m? Homework Equations torque (t) = NIABsintheta The Attempt at a Solution I'm not actually sure if this is even...
22. ### Time Constant, Resistance, Energy

Homework Statement A 11.0 uF capacitor in a heart defibrillator unit is charged fully by a 12000 V power supply. Each capacitor plate is connected to the chest of a patient by wires and flat "paddles," one on either side of the heart. The energy stored in the capacitor is delivered through...
23. ### Equivalent Resistance in series circuit

Homework Statement Three resistors with values of 7.0 Omega, 12 Omega, and 16 Omega are connected in series in a circuit with a 9.0 V battery. a) What is the total equivalent resistance? b) What is the current in each resistor? c) At what rate is energy delivered to the 16 Omega resistor...
24. ### RC Circuit find capacitor charge

Homework Statement The capacitor in an RC circuit (R = 130 \Omega, C = 40uF) is initially uncharged. 1) Find the charge on the capacitor in the circuit one time constant (tau = RC) after the circuit is connected to a 9.0- V battery. 2) Find the current in the circuit one time constant (\tau...
25. ### Battery connected to capacitors in series

Homework Statement A 12-V battery is connected to three capacitors in series. The capacitors have the following capacitances: 4.0uF, 14uF, and 33uF. Homework Equations R = V/I The Attempt at a Solution I'm thinking you add the capacitances since they are in series (do i need to...
26. ### Average current produced by pacemaker

Homework Statement Pacemakers designed for long-term use commonly employ a lithium-iodine battery capable of supplying 0.42 A*h of charge. b) If the average current produced by the pacemaker is 5.6 uA what is the expected lifetime of the device? Homework Equations C = A/s The...
27. ### Find the electric potential energy of this system of charges

Homework Statement A point charge q_1 = 86.5 uC is held fixed at the origin. A second point charge, with mass m = 5.90×10−2 kg and charge q2 = -2.95 uC, is placed at the location (0.323 m, 0) 1) Find the electric potential energy of this system of charges. 2)If the second charge is released...
28. ### Finding potential between plates

Homework Statement Determine the potential 1.0 mm from the negative plate of a pair of parallel plates separated by 4.0 mm and connected to a 24 V battery. Homework Equations w = EPEa - EPEb v = kq^2/r^2 The Attempt at a Solution I'm not exactly sure how to start. Can someone tell...
29. ### Electric charges/electric fields

Homework Statement Two electric charges are separated by a finite distance. Somewhere between the charges, on the line connecting them, the net electric field they produce is zero. 1) Do the charges have the same or opposite signs? Explain 2) If the point of zero field is closer to...
30. ### Point charges and magnitude of the electric field at the center of a triangle

Homework Statement A point charge q = 4.9 \mu C is placed at each corner of an equilateral triangle with sides 0.20 m in length. Is the magnitude of the electric field at the center of the triangle greater than, less than, or the same as the magnitude at the midpoint of a side? Explain...