pl help

satishinamdar

New member
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Jan 6, 2005
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14
Sir,
The problem reads as follows.I am not in a position .Kindly help.
A stone is thrown from a cliff of a mountain at a height of 171 ft. at velocity 17 ft/sec. What distance is short from a person standing at 228 ft from that person throwing a stone?
Is it a projectile example?
 
at what angle relative to the horizontal is the initial velocity of the projectile?

in what direction is the 228 ft relative to the person throwing the stone?

Is it a projectile example?

what do you think?
 
Hello, satishinamdar!

I assume that English is not your first language.
The problem is not clearly stated
\(\displaystyle \;\;\)but I will make some guesses . . .

A stone is thrown from a cliff of a mountain at a height of 171 ft. at velocity 17 ft/sec.
What distance is short from a person standing at 228 ft from that person throwing a stone?
From the nature of the problem, I would guess that it is a projectile example.

I will assume that the initial velocity is horizontal.
\(\displaystyle \;\;\)That's only way that it makes sense.

I also assume that the second person is standing 228 feet from the base of the cliff.
Code:
        A
        **→
        |   *
        |
    171 |     *
        |
        |
       -+-------*---------------*
        B   x   D               C
        :- - - - - 228 - - - - -:

The cliff is \(\displaystyle AB\,=\,171\) feet.
The stone is thrown from A with a horizontal velocity of 17 ft/sec.
The second person is at \(\displaystyle C\), 228 feet from \(\displaystyle B\).
The stone strikes the ground at \(\displaystyle D,\;x\) feet from \(\displaystyle B\).
We are asked for the distance \(\displaystyle DC\).

The horizontal position of the stone is: \(\displaystyle \,x\:=\:17t\)
The vertical position of the stone is: \(\displaystyle \,y\:=\:171\,-\,16t^2\)

It strikes the ground when \(\displaystyle y\,=\,0:\;171\,-\,16t^2\:=\:0\;\;\Rightarrow\;\;t\,=\,\frac{3\sqrt{19}}{4}\)

Then point \(\displaystyle D\) is at: \(\displaystyle \,x\:=\:17\left(\frac{3\sqrt{19}}{4}\right)\:\approx\:55.6\) feet.

Therefore, the stone lands \(\displaystyle \,228\,-\,55.6\:=\:172.4\) feet short.
 
Dear Soroban,
Thanks for reply .Can you please explain how is y=171-16t^2?

You are right in guessing that English is not my first language.Still as a curiosity I want to know from you , which mistake I did in writing.It will be a help to improve.
Regards and thanks .
I await your reply.
 
16t² is the distance the stone falls in t seconds. (s=(1/2)gt² where g=32 ft per second per second.) Since it starts at 171 feet it will be 171 - 16t² high after t seconds.

I am not in a position.
I would say
I am not able to solve it.
If you say "I am not in a position." you must say in a position to "do something". Position is not so much a wrong word, but it is not the word a "native" would use.


What distance is short from...
What distance is it short from...


Is it a projectile example?
"Is it an example of a projectile?"
would be prefered.
 
Dear Gene,
Thank you very much for explaining the proble.I also thank you for giving gramatically correct sentences.I was in a hurry and could not check the grammer.I also could not complete the sentence "I am not in a position ......

Even though English is not my first language, I do not make such mistakes.
Thank you once again.
 
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