Thera are a cylinder and a piston, both made of a thermal insulator, enclosing an ideal gas. An atom of the gas collides with the piston as shown below. The volume of the gas is reduced by lowering the piston. Will the speed of the gas as well as its temperature increase?
For a reference, I attach the original question as follows.
My attempt
For me, this question is not clear enough. Let me assume the pressure is kept constant. Based on the following relationship, $$ p=\frac{1}{3}\,\rho\, v^2_{\text{rms}} $$ decreasing volume will increase the density $\rho$ and decrease $v^2_{\text{rms}}$. And based on $$E_\text{k}=\frac{3}{2}\,k \,T$$ Decreasing speed will decrease the temperature. So my answer is both speed and temperature of the gas decrease when lowering the piston.
However, the answer key said otherwise, both increase.
Question
What is the correct answer?