Freefall-Type Question: Solving for Ball Catching and Building Length

  • Thread starter Iceman2032
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In summary, the conversation discusses a question about whether a ball dropped from the top of a tall building will be caught by another ball thrown downwards from the same building. The problem involves using equations for distance fallen in a certain time and setting them equal to each other to solve for time. The person asking for help has made some calculations, but is unsure if they are correct and is looking for guidance.
  • #1
Iceman2032
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I am really struggling with this question:

A ball is dropped from the top of a tall building. Exactly 2 seconds later, another ball is thrown downwards from the top of the same building at 25 m/s. Will the second ball catch the first ball? If so, what is the minimum length of the building? If not, what is their closest approach?

I do not need the full solution, just a hint. It seems that whatever I do gets to a dead end. From the 5 variables (d, t, initial v, final v, and acceleration) I only have 2 of them in both cases...initial velocity and acceleration (which is 10 m/ss...given) I have also sketched the graphs but I just don't get this question.

Any help is appericiated.
 
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  • #2
IF the 2nd one catches the first, then they would have the same displacement, wouldn't they? set two equations for d equal to each other and solve for time. If you get a negative answer, then "it can't happen."
 
  • #3
distance fallen in t seconds is x(t)= (g/2)t2+ v0t
where v0 is the initial velocity.
The "dropped" ball has initial velocity 0, the thrown ball has initial velocity 25 (I'm taking positive downward). Also, be careful about when t= 0 is. If you take t= 0 to be when the first ball is dropped, the time the second ball is falling is t-2. The second ball will catch up to the two when they both have the same "x" so set up the two formulas, set them equal, and solve for t.
 
  • #4
Okay, I took your suggestions and came up with the calculations attached to this post.

First of all excuse the typos and all, I just noticed an 'is' needs to be an 'if'. Took me some time to convert my scribbles into a neat image.

Now as you can see I have ended up with a negactive value for x. Something tells me I'm doing something really wrong. I mean the value of x is supiciously small...and negative. According to the first reply, they should never catch.

Also in my answer sheet, the answer to this problem is indicated as: 180m

It doesn't say wether 180 is their closest approach or height of the building.

So can you please tell me what I am doing wrong? Am I even using the right formula?! And after I calculate x, where do I go from there?

I really get lost in these 'catch' problems...
 

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  • #5
Nevermind, problem solved :)
 

What is a freefall-type question?

A freefall-type question is a type of scientific inquiry that involves dropping an object from a height and measuring its motion and acceleration due to gravity.

What is the purpose of a freefall-type question?

The purpose of a freefall-type question is to study the effects of gravity on an object and to gather data to better understand the laws of physics.

What equipment is needed for a freefall-type question?

The equipment needed for a freefall-type question typically includes an object to be dropped, a measuring device such as a timer or stopwatch, and a measuring tool such as a ruler or tape measure. In some cases, additional equipment such as a motion sensor or video camera may also be used.

What are some examples of freefall-type questions?

Some examples of freefall-type questions include: How does the mass of an object affect its rate of acceleration during freefall? How does air resistance impact the motion of an object in freefall? How does the height from which an object is dropped affect its final velocity?

What are the potential safety concerns when conducting a freefall-type question?

Some potential safety concerns when conducting a freefall-type question include making sure the area is clear of people and obstacles, wearing appropriate safety gear, and using caution when dropping heavy objects or from great heights. It is also important to follow proper laboratory safety protocols and to have a supervisor present when conducting experiments involving freefall.

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