Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    0
    ReputationRep:
    First one:

    A body of mass 5kg rests horizontally on a rough horizontal ground. It is being pushed with a force of 3N. The coefficient of friction between the body and the ground is 1/7.
    i) Find the magnitude of F.
    Finding Reaction Force:
    R - 5g = 5 x 0
    R = 5g

    Finding Friction:
    F = uR
    F = 1/7 x 49 = 7N


    ii) State whether the body will remain at rest or accelerate from rest along the ground.
    The body will remain at rest (because the friction force > pushing force) <--is that correct?




    Question 2:
    A small stone of mass 0.4kg is projected vertically upwards from the bottom of a pond full of water with speed 10m/s. As the stone moves through the water it experiences a constant resistance of magnitude 3N. Assuming that the stone does not reach the surface of the pond, find
    a) the greatest height above the bottom of the pond that the stone reaches
    u = 10
    v = 0
    t = ?
    a = ?

    I'm not sure which suvat formula to use here, any pointers?


    THANKS! +ve rep up for grabs
    Offline

    1
    ReputationRep:
    Your first ones are correct.

    For Question 2, try using f=ma to get the value of the acceleration. You are given f and m! Good luck.
    Offline

    18
    ReputationRep:
    First one is correct.
    Second one, is there a diagram or something showing a distance? If there is, v^2 = u^2 + 2as should work. If not, v = u + at having used F=ma to get acceleration should do.

    And your rep power is zero, btw.
    Offline

    11
    ReputationRep:
    for the second one do F = ma with F = -0.4g-3 and m = 0.4
    a = F/m = -9.8

    then v^2 = u^2 + 2as with v taken as 0 (when the particle reaches its max height it stops) gives
    0 = 100 + 2x-9.8xs
    100 = 19.6s
    s = 100/19.6 = 5.1m
 
 
 
  • 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
    Brexit voters: Do you stand by your vote?
    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

    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.