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Snowballs are thrown with a speed of 11 m/s from a roof 6.0 m above the ground. Snowball A is thrown straight downward; snowball B is thrown in a direction 20^\circ above the horizontal.
1-Find the direction of motion of the two snowballs just before they land.

  • phy -

    for ball A- it continues straight down

    for ball B:
    v= 11 sin 20 - g t
    h = 6 + 11 sin 20 t - 4.9 t^2
    when h = 0
    0 = 6 + 3.76 t - 4.9 t^2
    t^2 - .768 t - 1.22 = 0
    t = [ .768 +/- sqrt (.59+4.88) ]/2
    t = [ .768 +/- 2.33 ]/2
    t = 1.55 seconds
    v = 3.76 - 9.8 (1.55)
    v = -11.43 vertical speed
    u = 11 cos 20 = 10.33
    so speed at h = 0 = sqrt(11.43^2+10.33^2)
    and angle down from horizontal = tan^-1 (11.43/10.33)

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