View Full Version : IF increase in K.E  is of a body is 100% ,increase in momentum
 
 pushpa_bhagat
Oct 11, 2010, 08:27 AM
 FadedMaster
Oct 11, 2010, 08:51 AM
Please restate your question so that it can be understood.
 Unknown008
Oct 11, 2010, 10:04 AM
I assume what I'll be posting is what you are looking for... 
 
Let the initial kinetic energy be E.
 
E = \frac12 mv_1\ ^2
 
It increases by 100%, or doubles, to become:
 
E' = \frac12 mv_2\ ^2
 
Where E' = 2E
 
Now, comparing the two:
 
\frac{E'}{E} = \frac{\frac12 mv_2\ ^2}{\frac12 mv_1\ ^2} = \frac{v_2\ ^2}{v_1\ ^2}
 
Now, momentum is given by:
 
p = mv_1
 
p' = mv_2
 
\frac{p'}{p} = \frac{mv_2}{mv_1} = \frac{v_2}{v_1}
 
Substituting what we found earlier;
 
\frac{E'}{E} = \frac{p'^2}{p^2}
 
Since this equals 2;
 
\frac{p'^2}{p^2} = 2
 
\frac{p'}{p} = \sqrt2
 
Can you finish it now?
 
Post what you get!
 pushpa_bhagat
Oct 12, 2010, 02:11 AM
I want ans in % in this Q.    If increase in K.E is 300% , increase in momentum in % 
A.29%         B .100%        C .none 
Thank for 1st Q . Tell me this Q.
 Unknown008
Oct 12, 2010, 02:23 AM
Just change it into %... 
 
\sqrt2 = 100 \times 1.41 = 141%
 
 
When this equals to 3, we get:
 
\frac{p'}{p} = \sqrt{3}
 
\sqrt3 = 100 \times 1.73 = 173%
 pushpa_bhagat
Oct 14, 2010, 03:50 AM
Thant u Igot it