Phy 121
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A ball falls freely from rest at a height of 2 meters. Observations indicate that the ball reaches the ground in .64 seconds.
• Based on this information what is its acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
If the ball falls 2m in .64 seconds, its velocity will be 2/.64, or 3.12 m/s. Acceleration = change in velocity/ time = 30 m/s / .64 seconds = 46.87 m/s^2
your units are correct
However there is no such thing as 'velocity'. (actually there is, but for this course, since the unmodified term 'velocity' is so often misused, there isn't)
There is average velocity, initial velocity, change in velocity, final velocity and instantaneous velocity, but no such thing as just plain 'velocity'.
You 3.12 m/s is an average velocity.
It is unclear where you got 30 m/s, but that quantity seems to be unrelated to this problem.
Had that been in change in velocity, your calculation would have been OK.
#$&*
• Is this consistent with an observation which concludes that a ball dropped from a height of 5 meters reaches the ground in 1.05 seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
A ball dropped from 5 meters has a velocity of 5/1.05 = 4.76 m/s. Its acceleration would be 4.76/ 1.05 = 4.5 m/s^2
again you need to be more specific with the term 'velocity'
#$&*
• Are these observations consistent with the accepted value of the acceleration of gravity, which is 9.8 m / s^2?
answer/question/discussion: ->->->->->->->->->->->-> :
No. They are not. I’m not sure why they are not though.
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15 minutes
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