Mechanics help?

Announcements
    Offline

    3
    ReputationRep:
    (Original post by petrus123)
    OK, thanks! I'll give it a try.
    Awesome, good luck, see what you get and compare it to that of the bear
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by CheeseIsVeg)
    Awesome, good luck, see what you get and compare it to that of thebear
    OK, I'm just slightly confused about why @thebear has his contact force arrow pointing upwards (it says down on the lift), although I did that at first too, so maybe I missed something.
    Offline

    3
    ReputationRep:
    (Original post by petrus123)
    OK, I'm just slightly confused about why @thebear has his contact force arrow pointing upwards (it says down on the lift), although I did that at first too, so maybe I missed something.
    Be summoned the bear
    • Thread Starter
    Offline

    2
    ReputationRep:
    I know this should be ridiculously simple, but I'm not quite sure how to solve it. Could anyone help with the last bit?
    Offline

    3
    ReputationRep:
    (Original post by petrus123)
    OK, I'm just slightly confused about why @thebear has his contact force arrow pointing upwards (it says down on the lift), although I did that at first too, so maybe I missed something.
    the lift is pressing up against the passenger's feet. *
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by the bear)
    the lift is pressing up against the passenger's feet. *
    Yes, but how do we know that that force is 294N?
    Offline

    3
    ReputationRep:
    (Original post by petrus123)
    Yes, but how do we know that that force is 294N?
    she is not sinking into the floor or lifting up from the floor. with respect to the floor she is in equilibrium. *
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by the bear)
    she is not sinking into the floor or lifting up from the floor. with respect to the floor she is in equilibrium. *
    OK, thanks. But what about the 294N downward contact force? Sorry if I'm missing something.
    Offline

    3
    ReputationRep:
    (Original post by petrus123)
    OK, thanks. But what about the 294N downward contact force? Sorry if I'm missing something.
    since she is in equilibrium with respect to the floor the upwards and downwards forces must be equal. *
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by the bear)
    since she is in equilibrium with respect to the floor the upwards and downwards forces must be equal. *
    So you could then use 9.8(40+m)-T-294=3(40+m)?
    If so, how do you find T?
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by petrus123)
    So you could then use 9.8(40+m)-T-294=3(40+m)?
    If so, how do you find T?
    Anyone?
    Offline

    3
    ReputationRep:
    (Original post by petrus123)
    So you could then use 9.8(40+m)-T-294=3(40+m)?
    If so, how do you find T?
    if you mean T to be the force in the string then it is not relevant as there are two equal and opposite tensions in the string which cancel out. *
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by the bear)
    if you mean T to be the force in the string then it is not relevant as there are two equal and opposite tensions in the string which cancel out. *
    OK, thanks!
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by petrus123)
    So you could then use 9.8(40+m)-T-294=3(40+m)?
    If so, how do you find T?
    I solved the problem a while ago, but I came back to this because I'm curious as to why the 294N force is only included in the upwards direction in the diagram if it is actually in both directions (so that the girl is in equilibrium relative to the lift floor). Sorry if this is a stupid question and/or obvious.
 
 
 
Write a reply… Reply
Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: September 29, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Today on TSR
Poll
Does your body insecurities make you avoid PE or exercise?
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
Study resources

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.