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How do you find the speed of a particle which has ben projected upwards?

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  • 21-04-2017 8:26pm
    #1
    Rose2000
    Registered Users Posts: 4 ✭


    Hi. I have been given a question and im not sure how to go about it. A particle is fired from ground level with initial speed 8i+28j m/s. Find the two times when its speed will be 10 m/s. Any help and suggestions on how to do this would be greatly appreciated. Thanks.
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    #2
    Fathom
    Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators, Regional East Moderators, Regional Midlands Moderators, Regional Midwest Moderators, Regional Abroad Moderators, Regional North Mods, Regional West Moderators, Regional South East Moderators, Regional North East Moderators, Regional North West Moderators, Regional South Moderators Posts: 9,046 CMod ✭✭✭✭Fathom


    MOD: Moved to Mathematics.


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    #3
    Bit cynical
    Registered Users Posts: 2,338 ✭✭✭Bit cynical


    Here's a suggested way of working.

    Split the motion of the particle into two components: vertical and and horizontal. Model each of these separately.

    The horizontal component is simple. It will maintain its velocity as there is no force - and therefore acceleration - in this direction. It will maintain its horizontal component of 8i throughout.

    The vertical component is equivalent to throwing the vertically upwards with an initial velocity of 28j. As it is traveling it is subject to an acceleration of g downwards. This means that for every second it is in the air, the upwards velocity is reduced by g. On the way down g is added to the velocity every second.

    Write down an expression for the vertical component of velocity as a function of time.

    When that is done, all that needs to be done after that is to create an expression for the speed given both components of velocity, vertical and horizontal.

    Then solve that equation for speed = 10m/s.


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