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Anonymous
Anonymous asked in Science & MathematicsPhysics · 1 decade ago

Physics Help. A rescue plane flying horizontally at 250 km/hr wants to drop supplies to stranded hikers...?

a) A rescue plane flying horizontally at 250 km/hr wants to drop supplies to stranded hikers on a ridge 200 m below the plane. How far in advance of the position of the hikers must the supplies be dropped?

b) If the supplies are released 400 m in advance of the position of the hikers, what vertical velocity must they be given to land at the hikers' position?

ANSWERS:

a) 443.7 m

b) 6.50 m/s downward

2 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    (a)

    Let:

    x be the horizontal distance travelled by the supplies before they reach the ledge,

    y be the vertical descent to the ledge,

    u be the horizontal speed of the plane,

    t be the time for the supplies to fall,

    g be the acceleration due to gravity.

    x = ut

    y = gt^2 / 2

    250 km / hr = 2.5 * 10^5 / 3600 = 69.444 m/s.

    Eliminating t:

    x^2 = 2u^2 y / g

    = 2 * 69.444^2 * 200 / 9.81

    x = 443.4 m.

    (b)

    Let:

    u1 be the horizontal speed of the plane,

    u2 be the initial vertical downward speed given to the supplies.

    x = u1 t

    y = u2 t + gt^2 / 2

    Eliminating t:

    y = u2(x / u1) + (g / 2)(x / u1)^2

    u2 = [ y - (g / 2)(x / u1)^2 ] / (x / u1)

    = [ 200 - (9.81 / 2)(400 / 69.444)^2 ] / (400 / 69.444)

    = 6.47 m/s.

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    Lv 4
    5 years ago

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