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    Can someone please explain the methods to find the answers of these 2 questions? Thanks a lot.
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    (Original post by sarah99630)
    Can someone please explain the methods to find the answers of these 2 questions? Thanks a lot.
    For the first question, the mass is held in equilibrium, so the tension in the string is equal to the weight of the mass, T=Mg.

    Since the string is light and inelastic, the same tension acts on the ball at the other end. The ball is undergoing circular motion, with acceleration a=\dfrac{v^2}{r} (you should learn this).

    Therefore, what force needs to act on the ball for it to undergo that circular motion (think Newton's second law)? This force will just be the tension in the string. So then you will have two expressions for the tension, so you can make them equal to each other and rearrange to make M the subject.

    ---
    For the second question, you should first find the angle along the circle through which the car will have moved in 6 seconds.

    Spoiler:
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    If \omega = \dfrac{\pi}{2}, then \theta = \omega t = \dfrac{6\pi}{2} = 3\pi.


    Knowing the angle, you then know the position along the circle (it might help to convert from radians to degrees if you are unsure), and then it is a simple case of geometry.

    Please post your workings and feel free to ask for more help if you are still stuck
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    (Original post by K-Man_PhysCheM)
    For the first question, the mass is held in equilibrium, so the tension in the string is equal to the weight of the mass, T=Mg.

    Since the string is light and inelastic, the same tension acts on the ball at the other end. The ball is undergoing circular motion, with acceleration a=\dfrac{v^2}{r} (you should learn this).

    Therefore, what force needs to act on the ball for it to undergo that circular motion (think Newton's second law)? This force will just be the tension in the string. So then you will have two expressions for the tension, so you can make them equal to each other and rearrange to make M the subject.

    ---
    For the second question, you should first find the angle along the circle through which the car will have moved in 6 seconds.

    Spoiler:
    Show



    If \omega = \dfrac{\pi}{2}, then \theta = \omega t = \dfrac{6\pi}{2} = 3\pi.



    Knowing the angle, you then know the position along the circle (it might help to convert from radians to degrees if you are unsure), and then it is a simple case of geometry.

    Please post your workings and feel free to ask for more help if you are still stuck
    That was VERY very helpful!! Thank you sooo much!!
 
 
 
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