Turn on thread page Beta

M1 dynamics, inclined plane and normal reaction watch

    • Thread Starter
    Offline

    5
    ReputationRep:
    Hey guys, i was reading an example.

    "A box of mass 2 kg is pushed up a rough plane by horizontal force of magnitude 25N. The plane is inclined to the horizontal at angle of  10^\cdot . Given that the coefficient of friction between the box and the plane is 0.3, find the acceleration of the box."

    so they draw a diagram for me and i understand everything that is going on, but then they seem to be finding the normal reaction, though they phrase it as "resolving the perpendicular to the acceleration", they label the force as R, and i can tell by the way that they work it out that its the normal reaction, my only promblem is the fact that they do this  R-2gcos10^\cdot -25cos80^\cdot.

    So why are they including the horizontal force and calculating it as if it was a force on the inclined plane? and even it was in the inclined plane why does it affect the normal? It would be perpendicular to it and perpendicular forces can not affect one another.
    Offline

    10
    ReputationRep:
    25N is a "horizontal force" so needs to be resolved perpendicular and parallel to the plane. It's not acting up the slope of the plane.
    • Thread Starter
    Offline

    5
    ReputationRep:
    (Original post by vc94)
    25N is a "horizontal force" so needs to be resolved perpendicular and parallel to the plane. It's not acting up the slope of the plane.
    Exactly yet the book includes it into the equation as if it was acting up the slope which is confusing me.
    • Thread Starter
    Offline

    5
    ReputationRep:
    Actually i think i understand now the since the force is horizontal to the plane it is acting at an angle on the box, if we were resolving in the direction of acceleration up the slope then it would be 25cos10N degrees but since we are resolving perp to the plain then we use 25sin10N or 25cos80N.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: April 9, 2011

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?
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

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.