Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    Hi, can anyone help with this question?

    A box of mass 10kg is being pulled up a line of greatest slope of a rough plane that is inclned at an angle of 15 degrees to the horizontal. The coefficient of friction between the planes and the box is 0.25. At the instant when the box is moving at 10ms the rope pulling the box breaks. Find the further distance moved by the box before coming to rest.


    I first tried resolving but without the pulling frce this was useless.

    I have got the kinetic energy of the box when it is at 10ms to be 500J. Im thinking that kinetic enregy lost = gain in potential + friction.

    So 500 = mgh + Fr x (distance) Is this right? The problem I have is that h is measured vertically and friction is down the plane at 15 degrees.

    The answer is 10.2 which is 2(500/10g)
    Offline

    2
    ReputationRep:
    (Original post by Womble548)

    I have got the kinetic energy of the box when it is at 10ms to be 500J. Im thinking that kinetic enregy lost = gain in potential + friction.

    So 500 = mgh + Fr x (distance) Is this right? The problem I have is that h is measured vertically and friction is down the plane at 15 degrees.

    The answer is 10.2 which is 2(500/10g)
    h = sin15 S (h up, S along slope)

    500 = (10g)*0.25* cos15 * S + 10g * sin15 * S

    gives 23.6645 S + 25.36 S =500

    S = 10.2

    Aitch
    Offline

    15
    ReputationRep:
    (Original post by Womble548)
    Hi, can anyone help with this question?

    A box of mass 10kg is being pulled up a line of greatest slope of a rough plane that is inclned at an angle of 15 degrees to the horizontal. The coefficient of friction between the planes and the box is 0.25. At the instant when the box is moving at 10ms the rope pulling the box breaks. Find the further distance moved by the box before coming to rest.
    KE loss = (0.5)(10)(10^2) = (5)(100) = 500J
    PE gain = (10)(g)(xsin15), let x=the further distance travelled.
    F = UR = 0.25[10gcos15] = 2.5gcos15
    Work against Fr = 2.5gxcos15

    Using conservation of momentum:
    PE gain + Work against Fr = KE loss
    10gxsin15 + 2.5gxcos15 = 500
    x[10gsin15 + 2.5gcos15] = 500
    x = 500/[10gsin15 + 2.5gcos15]
    x = 10.2m
    • Thread Starter
    Offline

    0
    ReputationRep:
    Thanks!
    Offline

    0
    ReputationRep:
    hi are all the three of you doing the M2 paper tomoz... cause you guys are definately on the ball, and look very ready for it!!
    • Thread Starter
    Offline

    0
    ReputationRep:
    Me? I am not ready for it, what gave you that idea?

    I can do the simple questions and can apply the concepts (dont understand half of them though) but when it gets complex I am in trouble
    Offline

    1
    ReputationRep:
    lol i hate mechanics and i dnt get any of it!!!!!
    Offline

    12
    ReputationRep:
    Good luck to u all for M2 exam tomorrow
    Offline

    0
    ReputationRep:
    (Original post by BCHL85)
    Good luck to u all for M2 exam tomorrow
    thnx! are you doing it too?
    Offline

    15
    ReputationRep:
    I'm doing it tomorrow. Good luck everyone.
    I just need to ensure i don't rush or lose my composure. After taking M3 last week M2 shouldn't be so bad.
    Offline

    12
    ReputationRep:
    Yes I am. I got 87% last summer cuz of stupid mistakes and want to make it higher
 
 
 
Turn on thread page Beta
Updated: January 20, 2005

University open days

  • Heriot-Watt University
    School of Textiles and Design Undergraduate
    Fri, 16 Nov '18
  • University of Roehampton
    All departments Undergraduate
    Sat, 17 Nov '18
  • Edge Hill University
    Faculty of Health and Social Care Undergraduate
    Sat, 17 Nov '18
Poll
Have you ever experienced bullying?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Equations

Best calculators for A level Maths

Tips on which model to get

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

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.