Kinematics - How high is the balcony

  • #1

Homework Statement



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. Homework Equations

d= v1 Δt+ ½ a Δt2
v22= v12 + 2 aΔd

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?
 

Answers and Replies

  • #2
gneill
Mentor
20,913
2,862
Looks good.

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

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