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    The question is the following:

    A "car" of mass 1800kg in an amusement park moves through the lowest part of a loop of radius 8.5m at 22ms^-1.

    Draw a free body force diagram for the car at this moment and calculate the upward force of the rails on the car.

    I've attached what the diagram should look like according to the answers.

    The answer given is as follows:

    From Newton’s second law:
    (mv^2)/r = P - mg
    ? P= m (v^2/r + g)
    P =120 kN

    What I don't understand is:

    - what P is... I think its supposed to be the upward force of the rails on the car.
    - Why the first bit of the answer isn't (mv^2)/r + P = mg because the centripetal force surely acts radially inwards, therefore upwards according to the diagram, and P would also act upwards...

    Would really really appreciate any help that you could give me!!!!!!!!!!

    Thank you in advance !!!
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    (Original post by Ninachuuu)
    The question is the following:

    A "car" of mass 1800kg in an amusement park moves through the lowest part of a loop of radius 8.5m at 22ms^-1.

    Draw a free body force diagram for the car at this moment and calculate the upward force of the rails on the car.

    I've attached what the diagram should look like according to the answers.

    The answer given is as follows:

    From Newton’s second law:
    (mv^2)/r = P - mg
    ? P= m (v^2/r + g)
    P =120 kN

    What I don't understand is:

    - what P is... I think its supposed to be the upward force of the rails on the car.
    - Why the first bit of the answer isn't (mv^2)/r + P = mg because the centripetal force surely acts radially inwards, therefore upwards according to the diagram, and P would also act upwards...

    Would really really appreciate any help that you could give me!!!!!!!!!!

    Thank you in advance !!!
    mate, P is the tension in the rail that keeps the car in the circular motion..hence it is the tension that provides the centripetal force....the answer to the question is

    (MV^2)/r + mg..........basically this requires you to find the resultant force on the car......solve the equation I am pointed out..that should give you the answer..keep me updated..
 
 
 
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