## View Poll Results: What is answer the following question?

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# Thread: Help in speed problem please

1. hello i need help in solving this
Q)If the speed of a vehicle increases by 2 m/s,its kinetic energy is doubled,then original speed of the vehicle is
a)(sqrt of 2 )+1 m/s

b)2(sqrt of 2 -1)m/s
c)2(sqrt of 2 + 1 )m/s
d)sqrt of 2 (sqrt of 2 + 1)m/s
sqrt is square root of
please help me out
Thnx in advance  2.

3. What have you got so far?
We don't answer homework questions, but we'll help YOU arrive at the answers.  4. I found the answer as 2(sqrt of 2 + 1 )m/s i just want you to cross check it  5. Originally Posted by Rajnish Kaushik I found the answer as 2(sqrt of 2 + 1 )m/s
Not useful.
HOW did you arrive at that answer?  6. i just used the identity 1/2*m*(v+2)^2 = 1/2*m*v^2 * 2  7. 1/2*m*(v+2)^2 = 1/2*m*v^2 * 2 ie KE=PE  8. And did you check it?
E.g.:
2(sqrt of 2 + 1 )m/s = (2(1.414+1) = 4.828 m/ s,
Square that = 23.3.

New value = 6.828 (i.e. adding 2 m/ sec).
6.8282 = 46.6.

46.6/23.3 = 2.

Confirmed.  9. Originally Posted by Dywyddyr And did you check it?
E.g.:
2(sqrt of 2 + 1 )m/s = (2(1.414+1) = 4.828 m/ s,
Square that = 23.3.

New value = 6.828 (i.e. adding 2 m/ sec).
6.8282 = 46.6.

46.6/23.3 = 2.

Confirmed.
So i was right yeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eeeeeeeeeeeeeeeee  10. I've always found that plugging in the numbers and actually calculating them helps.  11. Originally Posted by Dywyddyr I've always found that plugging in the numbers and actually calculating them helps.
Thnx for advice please cart your vote above  Bookmarks
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