Physics

A penny is placed at the outer edge of a disk (radius = 0.159 m) that rotates about an axis perpendicular to the plane of the disk at its center. The period of the rotation is 1.50 s. Find the minimum coefficient of friction necessary to allow the penny to rotate along with the disk

  1. 👍
  2. 👎
  3. 👁
  4. ℹ️
  5. 🚩
  1. Hey, Do your homework. Look at your notes and read the book. We are watching you.
    Dr. C will not be happy.

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
  2. Static Friction Coefficient = Cfs
    For of Static Friction = Fs
    Normal Force = Fn
    Centripetal Force = Fc
    mass = m
    radius = r
    speed = v
    period of time = T

    Fs = Cfs * Fn so Cfs = Fs/Fn

    Fc = Fs and since Fs = mv^2/r

    Cfs = Fs/Fn = mv^2/r*Fn

    v = 2πr/T and Fn = mg

    so....

    mv^2 (2πr/T)^2 4(π^2)r
    Cfs = ------ = ----------- = --------
    rFn r(g) g(T^2)

    4(π^2)(0.159 m)
    Cfs = ------------------- = 0.28467
    (9.8 m/s^2)(1.50 s)^2

    *** Remember there are no units on coefficients***

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
  3. well that doesn't look readable. the answer should still be right but I'll rewrite how I did the math

    Cfs = mv^2/rFn = ((2πr/T)^2)/r(g) = (4(π^2)r)/g(T^2)

    Cfs = 4(π^2)(0.159 m) / (9.8 m/s^2)(1.50 s)^2 =
    0.28467

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩

Respond to this Question

First Name

Your Response

Similar Questions

  1. physics

    A 4.0 kg, 36-cm-diameter metal disk, initially at rest, can rotate on an axle along its axis. A steady 5.5 N tangential force is applied to the edge of the disk. What is the disk's angular velocity, in rpm, 4.0 s later?

  2. Physichs

    Two metal disks, one with radius R1 = 2.40 cm and mass M1 = 0.900 kg and the other with radius R2 = 4.95 cm and mass M2 = 1.50 kg , are welded together and mounted on a frictionless axis through their common center. A light string

  3. physics

    1.what is the final velocity of a hoop that rolls with out slipping down a 3.00m high hill starting at rest? 2. a 1.80 m radius playground merry go round (disk = 1/2 m r^2) hass a mass of 120 kg and is rotating with an angular

  4. Physics 203 ( College)

    A disk of radius 12 cm, initially at rest, begins rotating about its axis with a constant angular acceleration of 7.8 rad/s2. What are the following values at t = 4.0 s? (a) the angular velocity of the disk (b) the tangential

  1. Physics

    A small disk of radius R1 is mounted coaxially with a larger disk of radius R2. The disks are securely fastened to each other and the combination is free to rotate on a fixed axle that is perpendicular to a horizontal frictionless

  2. Physics

    Anybody help me with this? A disk with mass m = 6.5 kg and radius R = 0.41 m hangs from a rope attached to the ceiling. The disk spins on its axis at a distance r = 1.4 m from the rope and at a frequency f = 19.4 rev/s (with a

  3. Physics

    A rotating uniform-density disk of radius 0.6 m is mounted in the vertical plane. The axle is held up by supports that are not shown, and the disk is free to rotate on the nearly frictionless axle. The disk has mass 5.8 kg. A lump

  4. Physics

    A bug sits on the edge of a rotating disk. Later, the bug begins to move toward the center of the disk. Does the bug exert a torque on the disk?

  1. physics

    A curcial part of a piece of machinery starts as a flat uniform cylindrical disk of radius R0 and mass M. It then has a circular hole of radius R1 drilled into it. The hole's center is a distance h from the center of the disk.

  2. MATH

    A collar of Styrofoam is made to insulate a pipe. Find its volume The large radius is to the outer rim. The small radius r is to the edge of the insulation. Use π for 3.14. r = 3 in R = 5 in h = 18 in. Round 2 decimal places

  3. physics

    A torque of 12 N ∙ m is applied to a solid, uniform disk of radius If the disk accelerates at what is the mass of the disk?

  4. Physics

    A solid cylindrical disk has a radius of 0.18 m. It is mounted to an axle that is perpendicular to the circular end of the disk at its center. When a 40-N force is applied tangentially to the disk, perpendicular to the radius, the

View more similar questions or ask a new question.