4. एक लम्बे बाँस का - भाग लाल, भाग हरा, भाग
पीला रंगा है और शेष भाग सफेद है. यदि सफेद भाग
की लम्बाई 4 मीटर हो, तो पूरे बाँस की लम्बाई ज्ञात
करो-
(A) 8
(B) 10
(C) 9
(D) 12
Answers
Step-by-step explanation:
{ \huge \bf { \mid{ \overline{ \underline{Correct \: Question}}} \mid}}∣
CorrectQuestion
∣
A bullet of mass 20 grams is horizontally fired with a velocity 150m per second from a pistol of mass 2 kg what is the recoil velocity of the pistol ?
\huge{\bold{\underline{\underline{....Answer....}}}}
....Answer....
\huge{\bold{\underline{Given:-}}}
Given:−
Mass of Bullet (m) = 20 grams.
Velocity of the Bullet after Firing (u) = 150 m/s.
Mass of The Pistol (M) = 2 kg.
Let the recoil velocity of the Pistol be "v".
\huge{\bold{\underline{Explanation:-}}}
Explanation:−
From Law of Conservation of momentum,
Initial Momentum = Final Momentum.
\large{\boxed{\tt P_i = P_f}}
P
i
=P
f
But Before Firing, the whole system (Gun & Bullet) is at Rest.
Therefore, Initial momentum will be zero.
Then the equation becomes,
\large{\leadsto {\underline{\underline{\tt P_f = 0}}}}⇝
P
f
=0
Now, Formulating the Values of Final Momentum.
\large{\tt \leadsto mu + Mv = 0}⇝mu+Mv=0
M = Mass of Pistol.
m = Mass of Bullet.
u = Velocity of bullet.
v = Velocity of bullet.
Substituting the values
\large{\tt \leadsto 20 \times 10^{-3} \times 150 + 2 \times v = 0}⇝20×10
−3
×150+2×v=0
[Here Mass of bullet (m) is taken as 20 grams = 20 × 10⁻³ Kg.]
\large{\tt \leadsto 20 \times 150 \times 10^{-3} + 2v = 0}⇝20×150×10
−3
+2v=0
\large{\tt \leadsto 3000 \times 10^{-3} + 2v = 0}⇝3000×10
−3
+2v=0
\large{\tt \leadsto 3\times 10^3 \times \dfrac{1}{10^3}+ 2v = 0}⇝3×10
3
×
10
3
1
+2v=0
\large{\tt \leadsto 3 \times \cancel{10^3} \times \dfrac{1}{\cancel{10^3}}+ 2v = 0}⇝3×
10
3
×
10
3
1
+2v=0
\large{\tt \leadsto 3 \times 1 + 2v = 0}⇝3×1+2v=0
\large{\tt \leadsto 3 + 2v = 0}⇝3+2v=0
\large{\tt \leadsto 2v = - 3}⇝2v=−3
\large{\tt \leadsto v = \dfrac{- 3}{2}}⇝v=
2
−3
\large{\tt \leadsto v = \cancel{\dfrac{- 3}{2}}}⇝v=
2
−3
\huge{\boxed{\boxed{\tt v = - 1.5 \: m/s}}}
v=−1.5m/s
So, The Recoil velocity of the Pistol is 1.5 m/s.
Note:-
Negative sign of Recoil velocity indicates that the recoil velocity of the Pistol is opposite to the Motion of the Bullet.