Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Applied maths - mock

Options
  • 08-04-2009 1:14am
    #1
    Mutant_Fruit
    Closed Accounts Posts: 4,943 ✭✭✭


    I'm supposed to be giving grinds in applied maths to a friend of a friend. It's been a few years since my LC so I've forgotten bits here and there ;)

    So, hopefully an easy question, I'm looking at a mock paper from this year and q4b has two masses attached to a string, hung over a pulley.

    Mass 2 is resting on the ground and mass 1 is suspended in mid air beside the pulley. Mass 1 is then dropped (vertically) a distance of 3.5 metres, calculate how fast mass 2 leaves the ground.

    What I've forgotten is how to handle the speed of mass 1. So can anyone give me a quick run down on how I should be solving this, or point me to a solution. I doubt i need a full worked solution, but if you're bored you could throw that in ;)

    Thanks.

    p.s. also, if anyone did this exact question, the answer to part 2 is that the mass won't hit the ground, it'll stop after travelling 0.25 m down and then start going back up, right?


Comments

  • Options
    #2
    MathsManiac
    Registered Users Posts: 1,595 ✭✭✭MathsManiac


    Not sure if I'm picturing the thing correctly. If I am, the string is not taut at the start, and the released mass drops freely under gravity for 3.5 metres and then the string suddenly becomes taut. If this is indeed what you mean, then I suggest the following:
    - calculate the speed of the falling mass at the instant the string goes taut (using v^2 = u^2 +2gs)
    - if the system is efficient (inelestaic string, smooth pulley) this is then basically an impulse question. Calculate the impulse applied to the mass at rest by the "impact" of the falling mass, and that should give you the velocity required.


Advertisement