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5.Work, Energy, Power and Collision
easy
પદાર્થની ગતિઊર્જા $19\%$ જેટલી ઘટે છે. તો વેગમાનની પ્રતિશત ઘટાડો કેટલા .....$\%$ હશે ?
A
$20$
B
$15$
C
$10$
D
$5$
Solution
Let percentage decrease in momentum $= X \%$
Decrease in momentum $mv _1- mv _2= m \left( v _1- v _2\right)=(0.0 X ) mv 1$
we can write it like this – $v _2=(1-0.0 X ) v _1 \quad$….(1)
Change in $K E-\frac{1}{2} m \left( v _1^2- v _2^2\right)=0.19 \frac{1}{2} mv _1^2$
$\Rightarrow v _2^2=0.81 v _1^2$
By equation $(1)$ we get $(1-0.0 X )^2=0.81$
$\Rightarrow X =10$
Standard 11
Physics
