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Kinematics - How high is the balcony

  1. Apr 27, 2016 #1
    1. The problem statement, all variables and given/known data

    Marian, who is standing on her balcony, is surprised by a pigeon and throws a flowerpot up in the air at 2.1 m/s. It takes 3.0 s for the flowerpot to smash to the ground. The flowerpot experiences acceleration due to gravity of 9.81 m/s2 [down]. Determine how high Marian's balcony is and how fast the flowerpot was moving just before it smashed to the ground.

    2. Relevant equations

    d= v1 Δt+ ½ a Δt2
    v22= v12 + 2 aΔd

    3. The attempt at a solution

    Given:

    V1 = 2.1 m/s (up)

    a = 9.81 m/s2 (down)

    t= 3.0 s

    Determine how high Marians balcony is:

    Δd= v1 Δ t+ ½ a Δt2

    d= (2.1 m/s) (3.0s) - ½ (9.81 m/s2) (3.0s)2

    = -37.8 m
    Δd = 38 m
    Marian’s balcony is 38 m high.


    Calculate how fast the flowerpot was moving before it smashed to the ground:

    v22 = v12 + 2 aΔd


    v22 = (2.1 m/s)2 + 2 (9.81 m/s2) (38 m)


    v22 = √750


    v22= 27 m/s (down)


    The flowerpot was travelling 27 m/s (down) before it smashed to the ground.

    Is this correct?
     
  2. jcsd
  3. Apr 27, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    Looks good.

    You could also have determined the final velocity more directly via a formula for velocity given initial velocity, acceleration, and time.
     
  4. Apr 29, 2016 #3
    Ok thanks for the help :)
     
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