Q2

Q11

for Q2-

We know min velocity to complete circle in vertical circular motion is \sqrt{5gl}

Here g_{eff}=g+g=2g

so v_{min}=\sqrt{10gl}

And for Q11-

E=\frac{kx^2}{2}

differentiate wrt t both sides.

20=kx \frac{dx}{dt}

\frac{dx}{dt} = v_{a}-v_{b}

x is the strech in the spring.

x=0.1m

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