Find Velocity: Help Solve Ball Problem

[Prasun-rick]

So the question which is troubling me is as follows:
A ball is thrown vertically down with velocity of 5 m/s.With what velocity should another ball be thrown down after 2 seconds so that it can hit the 1st ball in next 2 seconds.

I couldn't ses the way out..as I feel the height of the 1st ball should be given...but I know I can be wrong..so please help me ..and thanks in advance.

 

[TSny]

The balls are thrown from the same spot. It doesn't matter how high that spot is above the ground as long as the spot is high enough that the first ball can be in flight for the required time before the second ball hits it. How long will the first ball have been in flight before the second ball hits it?

 

[Prasun-rick]

The balls are thrown from the same spot. It doesn't matter how high that spot is above the ground as long as the spot is high enough that the first ball can be in flight for the required time before the second ball hits it. How long will the first ball have been in flight before the second ball hits it?

welll...as far as I understood...the first ball was thrown vertically downwards and the second vertically upwards...and coming to your question the first ball would have stayed 4 sec in flight before the second one hits it...I guess :)

 

[Prasun-rick]

welll...as far as I understood...the first ball was thrown vertically downwards and the second vertically upwards...and coming to your question the first ball would have stayed 4 sec in flight before the second one hits it...I guess :)

But how to solve after that??..please help!

 

[TSny]

welll...as far as I understood...the first ball was thrown vertically downwards and the second vertically upwards...

The problem states that both balls are thrown downward.

and coming to your question the first ball would have stayed 4 sec in flight before the second one hits it...I guess :)

Yes. Good. What can you calculate that would be helpful in answering the question?

 

[Ray Vickson]

welll...as far as I understood...the first ball was thrown vertically downwards and the second vertically upwards...and coming to your question the first ball would have stayed 4 sec in flight before the second one hits it...I guess :)

Why do you claim that the second ball is thrown upwards. The question says, very clearly "... another ball be thrown down... "--so thrown down, not up.

 

[Prasun-rick]

The problem states that both balls are thrown downward.
Yes. Good. What can you calculate that would be helpful in answering the question?

Well yes...sorry It was my fault...indeed the second was thrown downwards too...
And I think I can calculate the distance they have traveled and also their final velocities !

 

[TSny]

And I think I can calculate the distance they have traveled and also their final velocities !

OK

 

[Prasun-rick]

Why do you claim that the second ball is thrown upwards. The question says, very clearly "... another ball be thrown down... "--so thrown down, not up.

yess...very sorry...It was my fault..I kept having a delusion that it was thrown upwards

 

[Prasun-rick]

OK

okay...then what to do?..Please help me out !..Should I equalise their distance travelled??..Will that be helpful?

 

[TSny]

You said you could calculate the distance traveled. Please show your work.

Note: Homework helpers are required to obey the Forum rules. One of the rules is not to help until the poster has filled out the template and shown some attempt at solving the problem. So, I'm already verging on getting fired here

 

[Prasun-rick]

You said you could calculate the distance traveled. Please show your work.

Note: Homework helpers are required to obey the Forum rules. One of the rules is not to help until the poster has filled out the template and shown some attempt at solving the problem. So, I'm already verging on getting fired here

okay thank you...I figured it out ..I just equalized the two distance !

 

[TSny]

okay thank you...I figured it out ..I just equalized the two distance !

Good work!