What is the average velocity of the object as it falls to the ground?

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Homework Help Overview

The discussion revolves around calculating the average velocity of an object dropped from a height of 25 meters. The problem involves concepts from kinematics, particularly the motion of freely falling objects under gravity.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the use of kinematic equations and the relationship between displacement, time, and velocity. There are attempts to clarify the correct formulas to use in the context of constant acceleration due to gravity.

Discussion Status

Some participants have provided guidance on using time of flight to find average velocity and have referenced relevant kinematic equations. However, there remains uncertainty about how to apply these equations correctly, and multiple interpretations of the problem are being explored.

Contextual Notes

Participants are questioning the accuracy of their calculations and the assumptions made regarding initial and final velocities. There is also a mention of a discrepancy between the calculated average velocity and a reference value from a textbook.

1irishman
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Homework Statement


An object is dropped from a height of 25m above the ground. What is the average velocity of the object as it falls to the ground?


Homework Equations


d=vit+1/2at^2


The Attempt at a Solution


d=-25
a=-9.8
vi=0

-25=-4.9t^2
t=2.3s
vavg=displacement/time
-25/2.3=-10.8m/s
the answer in book says a=-11.1m/s i don't understand, please help?
 
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Use the 2.3 s time of flight to find the velocity just before the object hits the ground. Half of that (because the starting velocity is zero) is the average velocity.
 
I still don't understand, how does that get plugged into the formula? What formula do I use?
Thank you
 
Use the kinematic equation that gives you the velocity of an object at any time t.
 
v=d/t right?
 
Nope. That equation is valid only when the acceleration is zero. Here the acceleration is g down. What equation do you know that relates the initial and final velocity to acceleration and time?
 
a=vf-vi/t right?
 
That's the one. You know everything except vf.
 

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