Hey there! Sign in to join this conversationNew here? Join for free

Mechanics 1 Help - finding mass of a weight on a pulley Watch

    • Thread Starter
    Offline

    0
    ReputationRep:
    I'm doing some past papers in preparation for my summer exams. I've come across a question which is asking for me to do something I haven't been taught in class nor is it in my revision guide.

    The question is:

    4) Two particles A and B are connected by a light inextensible string which passes over a smooth fixed pulley. A has mass 4kg and descends 2.8m in the first 2 seconds. after the system us released from rest, the hanging parts of the string being vertical. Find the mass of B and tension in the string.

    I've labelled mass B as 'mkg', which I have come across in previous questions, where it has asked me to find the acceleration instead of the mass. I know how to work out the tension, though I won't be able to do this until I know some more of the values.

    Thanks!
    Offline

    18
    ReputationRep:
    (Original post by rodstagraam)
    I'm doing some past papers in preparation for my summer exams. I've come across a question which is asking for me to do something I haven't been taught in class nor is it in my revision guide.

    The question is:

    4) Two particles A and B are connected by a light inextensible string which passes over a smooth fixed pulley. A has mass 4kg and descends 2.8m in the first 2 seconds. after the system us released from rest, the hanging parts of the string being vertical. Find the mass of B and tension in the string.

    I've labelled mass B as 'mkg', which I have come across in previous questions, where it has asked me to find the acceleration instead of the mass. I know how to work out the tension, though I won't be able to do this until I know some more of the values.

    Thanks!
    use suvat equations to work out the acceleration
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by gdunne42)
    use suvat equations to work out the acceleration
    that seems quite obvious. thanks!
    Offline

    18
    ReputationRep:
    (Original post by rodstagraam)
    that seems quite obvious. thanks!
    Yep if it's a question that you know is usually all about forces / acceleration and they tell you stuff about distances and times or velocities then there's going to be a bit of suvat in the solution.
    Offline

    0
    ReputationRep:
    Here's my answer, I think it's right, but don't take my word on it, as it's been many months since I've done M1.

    Name:  2013-04-14 15.09.37.jpg
Views: 81
Size:  274.4 KB
    Offline

    0
    ReputationRep:
    was it right? just out of pure curiosity?
    Offline

    18
    ReputationRep:
    (Original post by paulpaulpauln)
    was it right? just out of pure curiosity?
    I think you may have made an error solving your simultaneous equations

    By adding them together to eliminate T I get

    4g - mg = 5.6 + 1.4m
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you like to hibernate through the winter months?
    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

    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
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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