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? asked in Science & MathematicsPhysics · 8 years ago

physics help please help!!!!?

Physics help please??!?

A student drops a book out of a window in a tall building. If it took 1.51 seconds for the book to hit the ground, how high above the ground is the window? meters

What is the books maximum speed during flight? m/s

At what time does this occur? seconds

How high above the ground is the book when it is falling at a speed of 393cm/s? m

3 Answers

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  • 8 years ago

    hight: gravity is generaly an acceleration of 9.81m/s^2. therefore the distance is s=ut+0.5at^2 metres

    distance = 0.5 x 9.81 x 1.51^2

    distance = 11.18 metres

    Max speed : v=u+at , where V is final velocity, which is the fastest.

    v=0 + (9.81 x 1.51) = 14.81 m/s

    this occours after 1.51 seconds, as the greatest speed is gotten before it hits the ground.

    im not bothered answering the last q, its a bit of an effort, sorry :)

  • ?
    Lv 7
    8 years ago

    How about U doing the math on this one:

    h = 1/2gt² {where t = 1.51 s, g = 9.81 m/s²}

    Vf = √2gh {where h = answer above}

    t = √2h/g {where h = answer above}

    when book is falling at a V = 3.93 m/s:

    V = √2gH

    H = V²/2g {where V = 3.93 m/s}

  • Anonymous
    8 years ago

    x=Vit+1/2at^2

    x=1/2g(1.51^2)

    x=(4.9)(2.28)

    x= 11.2 m off the ground. (ANSWER)

    Maximum speed is Vf, so

    Vf=Vi+at

    Vf=(9.8)(1.51)

    Vf=14.8 m/s (ANSWER)

    This occurs at 1.51 s because it was right before impact.

    393 cm/s = 3.93 m/s

    V^2=2aX

    X=Vf^2/2a

    X=3.93^2/(2*9.8)

    X=0.79 m (ANSWER)

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