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

    0
    ReputationRep:
    A projectile is thrown upwards fom the edge of a cliff. It reaches a maximum height after 5 seconds ignoring air resistance and assuming g is 10's^2

    Calculate the maximum height of the projectile.

    So i know V=0 A=-10 and t = 5 trying to find X (displacment)

    so i use x=VT- 1/2 AT^2

    so i get x=-1/2 (-10) -1/2(5)^2 = -7.5 which is obv wrong so is the answer 7.5 and i put a minus in the (-5)?
    Offline

    2
    ReputationRep:
    (Original post by hazbaz)
    A projectile is thrown upwards fom the edge of a cliff. It reaches a maximum height after 5 seconds ignoring air resistance and assuming g is 10's^2

    Calculate the maximum height of the projectile.

    So i know V=0 A=-10 and t = 5 trying to find X (displacment)

    so i use x=VT- 1/2 AT^2

    so i get x=-1/2 (-10) -1/2(5)^2 = -7.5 which is obv wrong so is the answer 7.5 and i put a minus in the (-5)?
    The five should be a minus 5, and you said V=0, so it cancells down to x=0t - \dfrac{1}{2}at^2
    • Thread Starter
    Offline

    0
    ReputationRep:
    When i do this the answer is still -7.5 -1/2(-10) -1/2(-5)^2=-7.5
    Offline

    12
    ReputationRep:
    (Original post by hazbaz)
    A projectile is thrown upwards fom the edge of a cliff. It reaches a maximum height after 5 seconds ignoring air resistance and assuming g is 10's^2

    Calculate the maximum height of the projectile.

    So i know V=0 A=-10 and t = 5 trying to find X (displacment)

    so i use x=VT- 1/2 AT^2

    so i get x=-1/2 (-10) -1/2(5)^2 = -7.5 which is obv wrong so is the answer 7.5 and i put a minus in the (-5)?
    Should be a plus instead of minus, no? and why do you have two "1/2" in the final line?

    Spoiler:
    Show
    I get x=125 for my answer


    It looks like you haven't used the formula properly
    Offline

    13
    ReputationRep:
    Initial velocity = ?
    Final velocity = 0

    This was your mistake, try it again/

    For the equation x=ut+(a2^2)/2 you have taken the final velocity for intial. thats your mistake
    Offline

    2
    ReputationRep:
    (Original post by hazbaz)
    When i do this the answer is still -7.5 -1/2(-10) -1/2(-5)^2=-7.5
    x=vt-\dfrac{1}{2}at^2

    Then you sub in your (correct) values from the first post (A= -10, V=0 t=5)

    It shouldn't come out at -7.5 nor 7.5.
    • Thread Starter
    Offline

    0
    ReputationRep:
    [QUOTE=n_251]Should be a plus instead of minus, no? and why do you have two "1/2" in the final line?

    Spoiler:
    Show
    I get x=125 for my answer


    never mind i got what you mean now IM SUCH A FAIL I DONT DESERVE TO DO MATHS A LEVEL
    Offline

    2
    ReputationRep:
    (Original post by hazbaz)
    never mind i got what you mean now IM SUCH A FAIL I DONT DESERVE TO DO MATHS A LEVEL
    Nah, everyone has off days...
 
 
 
  • 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 rather give up salt or pepper?
    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.