# A speed problem

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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

Edited by Jay Sharma
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What's the equation for KE?

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there is no equation given for K.E

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there is no equation given for K.E

What is classical Kinetic Energy equation that you learn in the first class of physics?

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ok that is K.E=1/2 m*v2

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So equation to solve will be:

1/2*m*(v+2)^2 = 1/2*m*v^2 * 2

m is common, solve v.

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so i got v=2 so how do i find the correct option that isnt an option in question ##### Share on other sites

so i got v=2 so how do i find the correct option I entered it to OpenOffice

A column is velocity

B column is K.E. with v

C column is. K.E. with v+2

D column is C/2

See where they're crossing.. You should not guess, but calculate..

v^2-4*v-4=0

Edited by Sensei
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I entered it to OpenOffice

A column is velocity

B column is K.E. with v

C column is. K.E. with v+2

D column is C/2 Kinetic Energy table.png

See where they're crossing..

You should not guess, but calculate..

v^2-4*v-4=0

oh sorry i had taven -4 as +4 sorry for that

thank you sensai for your help

i found that the option c (c)2(sqrt of 2 + 1 )m/s)is correct please just crosscheck it once please

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and help me in other questions please

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V equal approximately 4.828 is the answer.

2* (sqrt(2)+1) = ~4.828

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V equal approximately 4.828 is the answer.

2* (sqrt(2)+1) = ~4.828

is that means i m right

if no then also help me

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!

Moderator Note

Members should be aware that the OP Jay Sharma has been banned as a sockpuppet of Rajnish Kaushik.

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