A monoatomic gas of mass 4.0 u is kept in an insulated container. Container is moving with velocity 30 m/s. If container is suddenly stopped then change in temperature of the gas ( R=gas constant) is  x3R. Value of  x is_________

The loss in Kinetic energy is converted into increase in internal energy of gas.Molar Mass of gas is given M= 4g/mol---(1)Let say mass of gas in container is mand moles of gas is n.nCv△T=12mv02 ⇒(n)3R2△T=12nM302∵n=mM  and for mono atomic gas,Cv=3R2, ⇒ΔT=4(900)3R=36003R             From equation (1)         Compare with x3Rwhich is given in question we get  x=3600