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    Luther2345's Avatar
    Luther2345 Posts: 2, Reputation: 1
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    #1

    Jan 9, 2012, 07:18 PM
    physics help grade 11?
    please help me with this questions thank you so much.
    1. A wave completes 44.8 cycles in 11.9 seconds. Find its speed if its wavelengh is 7.77 x 10^3 m?
    2. And object moving at 1.225m/s accelerates at 6.611m/s2 for 3.330s. Find work and power, if the object's mass is 55.5 kg?
    3. A boulder with m=339kg falls from the top of a cliff. It strikes the ground 2.24 seconds later.
    a) How long is the cliff?
    b)How much work did gravity do on the boulder as it fall to the ground?
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
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    #2

    Jan 9, 2012, 11:15 PM
    1. Find the frequency of the wavelength (that is the number of cycles the wave complete in one second.

    Then use to find the speed.

    2. You can work it out using energy. Find the initial kinetic energy. Find the final velocity to be able to get the final kinetic energy.

    With those two, you can get the work done on the object. And with the work done and time, you can get the power.

    3. a) Use s = ut + 0.5 at^2
    b) W = Fd

    It should be simple and straightforward.

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