Question

A 100gram bullet is fired from a gun with a speed of 1km/sec what is the mass of gun when speed of recoil of the gun is 20m/sec​

Answer 1

Given :

Mass of bullet = 100 g = 0.1 kg

Initial velocity = 1000 m/s

Final velocity =  20 m/s

mass of gun = ?

Answer :

A/c to Law of conservation of momentum ,

$\bold{m_i.v_i=m_f.v_f}$

where ,

$m_i=Initial \; mass=mass\;of\;bullet\;+\;mass\;of\;gun\;\\\\v_i=Initial\;velocity\\\\m_f=Final\;mass=mass\;of\;bullet\\\\v_f=Final\;velocity$

sub. the values in the formula we get ,

$\implies m_i.v_i=m_f.v_f\\\\\implies (0.1+m_g)1=0.1(20)\\\\\implies 0.1+m_g=2\\\\\implies\bold{ m_g=1.9\;kg}\\\\\implies \bf{\blue{\bold{mass\;of\;gun\;=1900\;grams}}}$