Turn on thread page Beta

Friction in Mechanics, how do I do this? watch

    • Thread Starter

    This is one question I haven't exactly done before:
    A builder holds up a vertical piece of particle having weight 40 N by pressing the two sides, force P Newtons with his hands. If mu = 1/4 (0.25) what is the least value of P needed if the particle is not to slip.
    I know, Friction = 1/2 W
    So Friction = 20N
    What do I do from here?
    • PS Helper

    PS Helper
    • Thread Starter

    That one liner is the one of the best

    F = uR
    (u = mew!)

    = 0.25 x 40 = 10N

    So in one direction (downwards) you have 40N.
    Friction acts in the opposite direction, with a magnitude of 10N.
    You want an overall force of magnitude 0N.
    P will act in the same direction as the friction; it's stopping this 'vertical particle' (wtf XD) from slipping down.
    So what is P?

    Edit: I think I may be wrong.

    First of all, the frictional force, is it per hand or what?
    Secondly, I'm not sure that R is 40N. I think R = P, or something.

    40 = P + 0.25R
    R = P
    40 = 1.25P
    P = 32N

    And if the frictional force is per hand, then:

    40 = P + 9.5R
    R = P
    40 = 1.5P
    P = 26.67N (2dp)

    At least one of these has to be right.
Submit reply
Turn on thread page Beta
Updated: January 27, 2010
The home of Results and Clearing


people online now


students helped last year

University open days

  1. SAE Institute
    Animation, Audio, Film, Games, Music, Business, Web Further education
    Thu, 16 Aug '18
  2. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  3. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
Do you want your parents to be with you when you collect your A-level results?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here


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

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