Turn on thread page Beta
    • Thread Starter
    Offline

    14
    ReputationRep:
    Need some help!

    Edexcel M2 ex 3C p74 q20

    20. A rough plane is inclined at arcsin 3/5 to the horizontal. A package of mass 40kg is released from rest and travels 15m while increasing speed to 12ms^-1. Find, using energy considerations, the coefficient of friction between the package and the plane.


    Answer = 0.138


    now what i thought was

    Work done against friction = energy lost/gained
    fs = pe lost - ke gained
    FS = mgh - 1/2mv^2

    f = mu(R)
    R = 40g4/5
    f = mu(40g4/5)

    mu(40g4/5)(15) = 3528 - 2880

    rearrange and mu = 2.something

    i tried anotherway and got 0.6... any ideas ?

    energy at top = energy at bottom + work done

    40*9.81*(3/5*15) = 1/2*40*12*12 + 15*F

    => F = 43.44 N

    μ = F/R = 43.44/(40*9.8*4/5) = 0.138
    • Thread Starter
    Offline

    14
    ReputationRep:
    (Original post by GeneralGrievous)
    energy at top = energy at bottom + work done

    40*9.81*(3/5*15) = 1/2*40*12*12 + 15*F

    => F = 43.44 N

    μ = F/R = 43.44/(40*9.8*4/5) = 0.138
    i could kiss you, man.

    but instead ive given you some rep.

    cheers

    *******s, looking back on what i did - i did it right; its just that i forgot to divide by the 15.... damn!
 
 
 
Poll
Do you think parents should charge rent?

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.