Motion In Two Dimensions Lab Question

AI Thread Summary
The discussion revolves around calculating the initial velocity of an object rolling off a table, given a height of 86 cm and a horizontal distance of 23 cm. Participants clarify that the time taken for the object to fall can be determined using the equation x = 1/2gt², leading to a calculated fall time of approximately 0.419 seconds. This time is then used to find the initial horizontal velocity, with initial estimates suggesting around 1.504 m/s. However, further calculations indicate that the correct horizontal velocity is closer to 0.6 m/s, as there is no horizontal acceleration involved. The conversation emphasizes the importance of distinguishing between vertical and horizontal motion in projectile motion problems.
Iokia
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Question and Data
What is the initial velocity of an object that rolls off a table and hits the floor below?
Lab produced the following data:
Table height: 86 cm
Distance of object from table when it hits floor: 23 cm

Relevant equations
Instantaneous Speed: Vf = Vo + at
[I think this is the correct one...]

The attempt at a solution
Gravity affects the object at a rate of 9.8 m/s.
Converting dimensions to meters:
86 cm = .86 m
23 cm = .23 m
I know gravity affects the height and the velocity affects the distance from the table and these two do not affect each other, but how do I determine the time?
You can't use sin and that triangle stuff because the object arches, it isn't straight.
I'd applicate any help or hints you could provide to help me threw this problem.
 
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Iokia said:
Question and Data
What is the initial velocity of an object that rolls off a table and hits the floor below?
Lab produced the following data:
Table height: 86 cm
Distance of object from table when it hits floor: 23 cm

Relevant equations
Instantaneous Speed: Vf = Vo + at
[I think this is the correct one...]

The attempt at a solution
Gravity affects the object at a rate of 9.8 m/s.
Converting dimensions to meters:
86 cm = .86 m
23 cm = .23 m
I know gravity affects the height and the velocity affects the distance from the table and these two do not affect each other, but how do I determine the time?
You can't use sin and that triangle stuff because the object arches, it isn't straight.
I'd applicate any help or hints you could provide to help me threw this problem.

Welcome to PF.

First figure the time for the object to fall .86m

x= 1/2g*t2

Then you know how far it went and for how long so figure how fast the horizontal velocity was and you're done.
 
Thank you.
x would really be the y displacement, which is .86m, correct?
So time is .419 seconds... and would you plug that into the displacement & time equation?
Which would give you 1.504 m/s as the initial velocity.

Thank you for your help.
 
Last edited:
Iokia said:
Thank you.
x would really be the y displacement, which is .86m, correct?
So time is .419 seconds... and would you plug that into the displacement & time equation?
Which would give you 1.504 m/s as the initial velocity.

Thank you for your help.

Isn't the distance .23m and the time .419s?
I get something quite less than 1.5 m/s at constant velocity.
 
If your looking for the x displacement. It turns out the same either way.
But yes, it is less than 1.5m/s. It's around .6, if I remember correctly. I plugged in gravity for the acceleration the second time but it's zero because their is no horizontal acceleration.

Thank you very much for your time.
 
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