Turn on thread page Beta
    • 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

    16
    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...
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: September 25, 2010

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.