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    Rinka's Avatar
    Rinka Posts: 5, Reputation: 1
    New Member
     
    #1

    Jul 2, 2003, 07:08 AM
    Momentum help
    ;D
    Sorry if I sound very stupid...

    A golfer hits a golf ball of mass 51g and the ball leaves the club with a velocity of 80m/s. Assuming that the ball and club are in contact for 0.0006s, find the ball's final momentum and the average force exerted by the club on the ball

    Next :
    diver dive from a height of 36m into the sea. Mass = 61kg.
    In a free-fall, before parachute is opened, diver reach terminal speed of 90m/s.
    Calculate force of air resistance on the diver when terminal speed

    :-[


    ________________ B
    / A
    __/__________________
    .. /
    .. /

    Velocity vs time graph
    A overtakes b t=0
    B accelerates and overtakes A
    What is the maximum distance between the cars before B catches up with A

    Why is it that part of the graph, (with dots)
    where both lines intersect
    I don't understand... can someone please explain??
    AHHH! Thank you
    :'(
    Dr._Ephemeron's Avatar
    Dr._Ephemeron Posts: 22, Reputation: 1
    New Member
     
    #2

    Jul 3, 2003, 02:42 AM
    Momentum help
    A.)

    Favg*delta_t = m*vt - m*v0

    v0 = 0

    delta_t = 0.0006 s

    m = 51E-3 kg

    vt = 80 m/s

    Favg = 51E-3*80/0.0006 = 6800 N

    p = m*vt = 51E-3*80 = 4.08 kg*m/s

    ----------------------------------------------------
    B.)

    SUM OF THE FORCES = MASS x ACCELERATION

    do a free body diagram of the sky diver with all the forces acting on him. He is at a terminal velocity so he is moving at a constant velocity. This means that the forces are equal all around him because he is not accelerating anymore.

    ----------------------------------------------------
    C.)

    I don't understand your graph but for constant acceleration:

    x = x0 + v0*t + 1/2*a*t2

    you want to set the equations for each moving object equal to the same point on the graph. You should be able to do that at 2 points giving you a system of 2 equations with 2 unknows.

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