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

    20
    ReputationRep:
    Name:  Screen Shot 2017-06-19 at 21.44.31.png
Views: 17
Size:  24.0 KB
    for part A)
    why is it
    T - mgsintheta + fmax = ma
    i thought it would be T - mgsintheta - fmax = ma ?
    Offline

    22
    ReputationRep:
    (Original post by ihatePE)
    Name:  Screen Shot 2017-06-19 at 21.44.31.png
Views: 17
Size:  24.0 KB
    for part A)
    why is it
    T - mgsintheta + fmax = ma
    i thought it would be T - mgsintheta - fmax = ma ?
    Clearly you are resolving up the plane. Also clearly, left alone the package slides down the plane. Friction opposes motion. So friction acts up the plane. So it is positive are you are resolving upwards.
    • Political Ambassador
    • Thread Starter
    Offline

    20
    ReputationRep:
    (Original post by Zacken)
    Clearly you are resolving up the plane. Also clearly, left alone the package slides down the plane. Friction opposes motion. So friction acts up the plane. So it is positive are you are resolving upwards.
    thanks for clearing it up
    Offline

    22
    ReputationRep:
    (Original post by ihatePE)
    thanks for clearing it up
    Sure. Do you see why that same chain of reasoning means that friction acts down the plane in (b)?
    • Political Ambassador
    • Thread Starter
    Offline

    20
    ReputationRep:
    (Original post by Zacken)
    Sure. Do you see why that same chain of reasoning means that friction acts down the plane in (b)?
    yes i do, friction opposes motion.
    sorry quick question,
    Name:  Screen Shot 2017-06-19 at 22.03.35.png
Views: 17
Size:  25.7 KB

    how would u find the area of the triangle really simply? the markscheme says 3*4 = 12
    but i went to do cosine rule and then 1/2 * b*c*sinA which is long winded for 7 marker. i dont see why they 3*4, and where they get the numbers from
    Offline

    22
    ReputationRep:
    (Original post by ihatePE)
    how would u find the area of the triangle really simply? the markscheme says 3*4 = 12
    but i went to do cosine rule and then 1/2 * b*c*sinA which is long winded for 7 marker. i dont see why they 3*4, and where they get the numbers from
    Slice the triangle down halfway from the vertex. This gives two equal right-angled triangles, each with base 3, hypotenuse 5 and so height 4. Hence has area \frac{1}{2} \times 3 \times 4 \times 2 (since there are two such triangles).

    Edit: In case this still isn't clear, the reason why each triangle has a base of 3 is because it's slices the side of the square in half, which has length 6.
    • Political Ambassador
    • Thread Starter
    Offline

    20
    ReputationRep:
    (Original post by Zacken)
    Slice the triangle down halfway from the vertex. This gives two equal right-angled triangles, each with base 3, hypotenuse 5 and so height 4. Hence has area \frac{1}{2} \times 3 \times 4 \times 2 (since there are two such triangles).

    Edit: In case this still isn't clear, the reason why each triangle has a base of 3 is because it's slices the side of the square in half, which has length 6.
    o right pythagorous, thank u so much.
    Offline

    18
    ReputationRep:
    (Original post by ihatePE)
    thanks for clearing it up
    could you say what the answer is. I have M1 tomorrow and I'm quite stressed.
    • Political Ambassador
    • Thread Starter
    Offline

    20
    ReputationRep:
    (Original post by AspiringUnderdog)
    could you say what the answer is. I have M1 tomorrow and I'm quite stressed.
    https://mathsbedwas.wikispaces.com/f...9729/Jun09.pdf <--- mark scheme (question 5) says 11.82N
    i have m1 tomorrow too, good luck
 
 
 
  • 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
    What newspaper do you read/prefer?
    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.