Read about phy homework | 25 Discussions | Page 1

  1. plomeiko

    Question about gravitational potential energy and angular motion

    hello I would like some help with the first part of this homework. for the moment i have done this: E initial=m*g*h Efinal= 1/2 m*v ^ 2+1/2I*ω ^ 2 Ei=m*g*h+1/2I*ω ^ 2 Ef=1/2*m*v ^ 2 my doubt is with the potential energy since it confuses me when there is or not
  2. M

    Find the area and length of a gold leaf

    Homework Statement Gold, which has a density of 19.32 g/cm3, is the most ductile metal and can be pressed into a thin leaf or drawn out into a long fiber. (a) If a sample of gold with a mass of 3.872 g, is pressed into a leaf of 5.372 μm thickness, what is the area of the leaf? (b) If...
  3. Penguin98

    The thickness of glass and the longest wavelength

    Homework Statement In your research lab, a very thin, flat piece of glass with refractive index 2.00 and uniform thickness covers the opening of a chamber that holds a gas sample. The refractive indexes of the gases on either side of the glass are very close to unity. To determine the thickness...
  4. A

    Help Please -- Calculate force at CG & away from CG

    Homework Statement Hello All, Please help me to find the force required to rotate a body of 4 Kg mass from 0° to 90° in 5 second. this force is acting at center of gravity. (Image: case 1) CASE-2: Force acting away from center of gravity. (Image: case 2) Homework Equations The Attempt at...
  5. J

    A Physics 11 Elevator Work/Power Problem

    Homework Statement An elevator takes a 70 kg person from street level to the top of a 400 m sky-scraper in 4 minutes. The mass of the elevator is 500 kg. a] At what rate is the elevator plus the person gaining potential energy? b] What power is the elevator plus the person experiencing as...
  6. SmugBug

    What is the angle of incidence?

    Homework Statement A light ray shines from a diamond (n = 2.42) into water (n = 1.33), and no refraction occurs. What is the angle of incidence? 0° 30° 45° 60° Homework Equations sin θc = nr/ni ? The Attempt at a Solution I thought that by finding the critical angle then anything...
  7. SmugBug

    How many air molecules are there inside the tire?

    Homework Statement A car tire has a volume of 10 L and is inflated to a gauge pressure of 30 psi (207,000 Pa) at 20°C. How many air molecules are there inside the tire? Homework Equations N = PV/ kbT The Attempt at a Solution (207,000 Pa )x (0.01 m3) / (1.38 x 10^-21 x 293) =5.12 x...
  8. H

    New wave after superposition (interference)

    Homework Statement 1. Homework Statement [/B] The displacement y of standing wave that is obtained by a superposition of waves : Y1 = 3 sin (2##\pi##(0.5t - 0 25 x)) Y2 = 3 sin (2##\pi##(0.5t + 0 25 x)) Homework Equations Formula for standing waves Y = 2Asinkx coswt The Attempt at a Solution...
  9. H

    Magnetic field and flux

    Homework Statement [/B] There is lead XY shaped as straight wire. Next to it, circular lead with radius 0.10 m. They are in the same plane. XY to center of circle, O is 0.20 m. Curent flowing through XY is 15.7 A Homework Equations The Attempt at a Solution 1) find magnetic field (B) at...
  10. O

    A Capacitor with initial charge

    Homework Statement A capacitor with initial charge q0 is discharged through a resistor. What multiple of the time constant τ gives the time the capacitor takes to lose (a) the first 1/8-th of its charge (b) 7/8-th of its charge? Homework Equations The Attempt at a Solution since ı know...
  11. H

    How to find the power consumed by the light bulb

    Homework Statement (Is the image read-able now? ) The fig 1 shows the relationship between voltage and current when voltage is applied to a certain light bulb. Next, in fig 2, the bulb is connected in series with a 12-V battery and a 5 ohm resistor. Question : what is the amount of power...
  12. K

    Block sliding up an inclined plane

    1. The problem statement, all variables, and given/known data A block with an initial speed of 20.0m/s slides up a ramp with an incline angle of 30º. (a) (2 points) Write the position as a function of time for motion up the surface of the ramp. (b) (2 points) Write the velocity as a function...
  13. lz975545

    Electric potential at the bottom of a ring?

    Homework Statement [/B] A circular ring of radius "a" has a total charge Q uniformly distributed along the top half. (Q is distributed along the semicircle in quadrants I and II). What is the potential at a point located on the bottom of the ring (observation point is on the ring in quadrant...
  14. J

    Finding the Spring Constant

    Homework Statement Force Extension in (m) 1.0 0.014. 1.5 0.032. 2.0 0.053. 2.5 0.071. 3.0 0.090. 3.5 0.110. 4.0 0.130. 4.5 0.148. 5.0 0.166...
  15. mh_99

    Find angle and seconds

    Homework Statement A football punter can punt a maximum range of 40.8 m. If he instead wants to punt only 34.6 m, but maximize the time the ball is in the air, at what angle from the horizontal should he kick the ball, and how long will it stay in the air if he hits it perfectly? (neglect air...
  16. R

    Masses connected to spring momentum

    Homework Statement An m = 1.3 kg block and an M = 3.0 kg block have a spring compressed between them and rest on a frictionless table. With a stopper in place that prevents m from moving, the spring is compressed and released so that M moves away with a speed 2.0 m/s. The spring is...
  17. R

    Block sliding on top of cart

    Homework Statement A block of mass m =0.75 kg is set on a large cart of mass M = 6.5 kg. The cart's rollers are frictionless, but there is a coefficient of kinetic friction of 0.36 between the cart's surface and the block. The cart is at rest when the block is given an initial speed of 5.2...
  18. T

    How to find the FWHM-diameter of the SH beam?

    Homework Statement Assume a Gaussian laser beam ( 1064 nm wavelength) having an FWHM-diameter(intensity) of 5 mm. By transmission through a thin nonlinear crystal, a new wave is generated that is proportional to the square of the incoming field (and therefore radiates at twice the frequency, or...
  19. S

    Solve questions on oscillations and kinetic energy

    A spring of spring constant k sits on a frictionless horizontal table, one end of the spring is attached to a wall the other end to a block of mass M= 2kg, also resting on the frictionless table. Another block of mass m=450g moving at a speed of 7m/s collides in-elastically with the block of...
  20. G

    Centre of mass of this boomerang?

    Homework Statement I have an image with the question here: http://imgur.com/TGG9VTx.jpg The red text is the answer. I havent been able to get it without contradicting what Ive been told. Homework Equations I know m1x1 + m2x / m1+m2 is centre of mass in 2d plane, but I dont know how that...
  21. G

    How does mass of the bungee jumper effect a safe jump

    Homework Statement physics major practical, I was supposed to change the mass and find how it effects the safety of the jumper.But since hooks law doesn't follow bungee cord i really cant find a relationship. Homework Equations The Attempt at a Solution I used a bungee cord and hung...
  22. S

    Simple Harmonic Motion equation rearrangement?

    Homework Statement Hello! I have a physics homework question I just need help at! What I am supposed to do is calculate the value for free-fall acceleration, ag, for each of my trials that I did in my lab. I supposed to use the equation for the period of the simple pendulum, T=2π√l/g, but I...
  23. V

    Delta Dirac 3d Dimensional Analysis

    1. I ´m trying to do the dimensional analysis of the Delta Dirac in 3 Dimensions. [PLAIN]http://[url=http://postimg.org/image/oif09fcd5/] 3. This is my atempt [PLAIN]http://[url=http://postimg.org/image/4qavbtv4p/]
  24. UF6

    Surface Density of a Charge

    Homework Statement You've probably noticed that TV screens and computer monitors have an annoying tendency to accumulate dust. Wanting to understand this better, you decide to model the situation as follows: you assume a small mote of dust might have an excess charge of 1 nC and a mass of 5...
  25. pdaniel

    Physics 12 Help

    Homework Statement Earth actually has an electric field of 1.0 x 10^2 N/C at its surface pointing toward the center. (b) Compare Earth's electric field and gravitational field in terms of i) direction ii) shape iii) how it changes as height increases. c) What is the largest mass that can be...
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