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

    6
    ReputationRep:
    2. A small stone is projected vertically upwards from a point O with a speed of 19.6msí1.
    Modelling the stone as a particle moving freely under gravity,
    (a) find the greatest height above O reached by the stone,
    (2)
    (b) find the length of time for which the stone is more than 14.7 m above O.


    I don't understand why v= 19.6 for part b, shouldnt it be 0 at the maximum height.

    Thanks in advance
    Offline

    22
    ReputationRep:
    (Original post by James_pa)
    2. A small stone is projected vertically upwards from a point O with a speed of 19.6msí1.
    Modelling the stone as a particle moving freely under gravity,
    (a) find the greatest height above O reached by the stone,
    (2)
    (b) find the length of time for which the stone is more than 14.7 m above O.


    I don't understand why v= 19.6 for part b, shouldnt it be 0 at the maximum height.

    Thanks in advance

    I think you're confused. This has nothing to do with the maximum height. Imagine the path of the projectile, it goes up, crosses the 14.7 metre mark (start your stopwatch!) continued upwards, hits the maximum height, start moving downwards, crosses the 14.7 metre mark again (stop your stopwatch!) and then hits the ground.

    You want the time that your stopwatch has recorded. Nothing to do with the maximum height, picture below:



    Standard way to do this is to find the times at which the particle is at 14.7 and then subtract the two times.

    To do so, set 14.7 = ut + 1/2at^2 and then solve the quadratic equation in t to get two solutions. Bigger solution - smaller solution = time.
 
 
 
  • 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's your favourite Christmas sweets?
    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.