Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    A light elastic string AB has nat. length l and modulus (20mg)/3 the end A is fixed and a particle of mass m is attached to end B

    the particle is made to move in a horizontal circle at constant angular speed with the string inclined at an angle arcsin(4/5) to eh vertical. Find in terms of l and g the angular speed of the particle.


    the answer is 2(g /3l )^1/2
    (i.e 2 times the sq rt of g over 3l)
    Offline

    2
    ReputationRep:
    Resolve upwards: TcosQ = mg (Q=theta)

    sinQ = 4/5, so cosQ = 3/5
    so, 3T/5 = mg

    T=(lambda)(e)/L = (20mg/3)(e) / L

    (3/5)(20mg/3)(e) / L = mg

    e=L/4
    so length of string = 5L/4

    F=ma
    TsinQ = mr(w^2)
    eventually: w^2 = 4(g/3L)

    so w = 2(g/3L)^1/2
    • Thread Starter
    Offline

    0
    ReputationRep:
    wat does r equal though? cuz i got uptil that point but then i cudnt find the radius r
    Offline

    2
    ReputationRep:
    (Original post by chetan)
    wat does r equal though? cuz i got uptil that point but then i cudnt find the radius r
    sinQ = r/(5L/4) = 4r/5L

    so you get T(4r/5L) = mr(w^2)
    now the r's can cancel, and so on.....
    hope it makes sense now.
    • Thread Starter
    Offline

    0
    ReputationRep:
    ye thats wat i 4got. thanx a lot
 
 
 

University open days

  1. University of Cambridge
    Christ's College Undergraduate
    Wed, 26 Sep '18
  2. Norwich University of the Arts
    Undergraduate Open Days Undergraduate
    Fri, 28 Sep '18
  3. Edge Hill University
    Faculty of Health and Social Care Undergraduate
    Sat, 29 Sep '18
Poll
Which accompaniment is best?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.