NCERT Solutions for Class 11 Science Newton’s law of motion and friction 3
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Newton’s law of motion and friction
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3 Marks Questions & Numericals
A hunter has a maching gun that can fire 50g bullets with a velocity of 150 ms⁻¹. A 60 kg tiger springs at him with a velocity of 10 ms⁻¹. How many bullets must the hunter fire into the target so as to stop him in his track ?
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Given m = mass of bullet = 50 gm = 0.50 kg
M = mass of tiger = 60 kg
v = Velocity of bullet = 150 m/s
V = Velocity of tiger = – 10m/s
(∴ It is coming from opposite direction n = no. of bullets fired per second
at the tiger so as to stop it.)
Pi = 0, before firing …(i)
Pf = n(mv) + MV …(ii)
∴ From the law of conservation of momentum,
Pi = Pf
⇒ 0 = n(mv) + MV
⇒ n = MV/mv
= -60/(-10)/0.05×150 = 80.