Kinematics Question: Falling object

In summary: In this case, the answer for part a) would be 38 m and part b) would be -27 m/s, both with a ±5% uncertainty.
  • #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/s [down].

a) How high is Marian’s balcony?

b) How fast was the flowerpot moving just before it smashed to the ground?

Homework Equations


For a) I believe I"m using ##\vec d = v_1 \Delta t + \frac 1 2 \vec a \Delta t^2##

for b) ##\vec v_2 = \vec v_1 + \vec a \Delta t##

The Attempt at a Solution


a) ##\vec d = (2.1 m/s) (3.0s) + \frac 1 2 (-9.81 m/s^2 [down]) (3)^2
\\ = 6.3 - 44.145
\\ = -37.84 [down]##

Balcony is 37.8 meters high

b) ## \vec v_2 = 2.1 + (-9.81 m/s^2 [down]) (3.0s)
\\ = -27.33 m/s [down]##

Pot was falling at 27.3 m/s when it hit the ground.Or if I'm correct with a) is it that I should just divide 37.8 by 3 to get 12.6?
 
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  • #2
Your method is perfect.

Catchingupquickly said:
Or if I'm correct with a) is it that I should just divide 37.8 by 3 to get 12.6?
That gives the average speed, not the final speed.
 
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Likes scottdave
  • #3
Ah. I see. Thank you!
 
  • #4
One thing to add, if this is an application where significant figures is important, then take note that answers should be limited to two significant figures.
 

1. What is kinematics?

Kinematics is the branch of physics that studies the motion of objects without considering the causes of the motion.

2. How is the motion of a falling object described in kinematics?

In kinematics, the motion of a falling object is described using equations that relate the object's position, velocity, and acceleration.

3. What is the acceleration of a falling object?

The acceleration of a falling object is 9.8 meters per second squared, commonly known as the acceleration due to gravity.

4. How does the mass of a falling object affect its motion?

The mass of a falling object does not affect its motion. All objects, regardless of mass, experience the same acceleration due to gravity.

5. What is the formula for calculating the velocity of a falling object?

The formula for calculating the velocity of a falling object is v = gt, where v is the final velocity, g is the acceleration due to gravity, and t is the time the object has been falling.

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