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

    2
    ReputationRep:
    2 forces (4i-2j)N and (2i+qj)N act on a particle P of mass 1.5kg. The resultant of these 2 forces is parallel to the vector (2i+j)
    fin the value of q

    so far i've done this

    4i-2j+2I+qj= 6i+(q-2)j

    i know that if a vector is parallel to another, it must be a scalar multiple of each other

    thus 2i+j multiplied by 3 = 6i+3j

    q-2=3
    q=5

    is this right?
    Zacken
    Offline

    22
    ReputationRep:
    (Original post by Steelmeat)
    is this right?
    Zacken
    Yes.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Zacken)
    Yes.
    The second part of this question is
    at time t=0 P is moving with velocity (-2i+4j)ms^{-1}
    Find the speed of P at time t=2 seconds

    so initial position vector is (-2i+4j) and i'm not sure what to do from there

    Edit: wait a second f=ma i have the mass and i have a resultant force (6i+3j) so i can get acceleration, so i can do this question?
    F=ma
    (6i+3j)=1.5a
    a= (4i+2j)???

    so v=(-2i+4j)+2(4i+2j)
    so the speed of P after 2 secs would be
    (6i+8j)???
    • Thread Starter
    Offline

    2
    ReputationRep:
    notnek is that right?? ^^
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Steelmeat)
    The second part of this question is
    at time t=0 P is moving with velocity (-2i+4j)ms^{-1}
    Find the speed of P at time t=2 seconds

    so initial position vector is (-2i+4j) and i'm not sure what to do from there

    Edit: wait a second f=ma i have the mass and i have a resultant force (6i+3j) so i can get acceleration, so i can do this question?
    F=ma
    (6i+3j)=1.5a
    a= (4i+2j)???

    so v=(-2i+4j)+2(4i+2j)
    so the speed of P after 2 secs would be
    (6i+8j)???
    It's nearly right but notice the question asks for speed and not velocity...
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by notnek)
    It's nearly right but notice the question asks for speed and not velocity...
    i see well i tripped up there
    so speed is 10ms^{-1} right?
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Steelmeat)
    i see well i tripped up there
    so speed is 10ms^{-1} right?
    Correct
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by notnek)
    Correct
    sorry to bother you again but

    can i say that |v|=10ms^{-1}?
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Steelmeat)
    sorry to bother you again but

    can i say that |v|=10ms^{-1}?
    Yes that's fine.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by notnek)
    Yes that's fine.
    thanks
 
 
 
  • 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.