JEE Main 2022 · 26 Jun · Shift 1 · Physics Q39

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PhysicsSingle correct+4 / -1Question 39 of 90

A thermally insulated vessel contains an ideal gas of molecular mass M and ratio of specific heats 1.4. Vessel is moving with speed $v$ and is suddenly brought to rest. Assuming no heat is lost to the surrounding and vessel temperature of the gas increases by :

(R = universal gas constant)

\dfrac{Mv^2}{7R}

\dfrac{Mv^2}{5R}

2\dfrac{Mv^2}{7R}

7\dfrac{Mv^2}{5R}

Answer and worked solution

Official answer: B

Kinetic energy becomes internal energy. Per mole, $\frac12Mv^2=C_v\Delta T$ with $C_v=\frac R{\gamma-1}=\frac52R$ .

So $\Delta T=\dfrac{Mv^2}{5R}$ .

(B)

Topics:Specific heats of gases First law and internal energy

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JEE Main 2022 · 26 Jun · Shift 1, Physics question 39