If the mass of the bob in a simple pendulum is increased to thrice its original mass and its length is made half its original length, then the new time period of oscillation is $\frac{x}{2}$ times its original time period. Then the value of $x$ is:
Answer & explanation
Correct answer: option 2
The correct answer is option (2) : $\sqrt{2}$
The period of oscillation, $T$, of a simple pendulum is determined by the formula :
$T=2\pi \sqrt{\frac{L}{g}}$
where :
$L$ is the length of the pendulum
$g$ is the acceleration due to gravity
The mass of the bob does not factor into the equation for the period.
Let's first denote the original length of the pendulum as $L$ and the original period of oscillation as $T_1$. Hence,
$T_1=2\pi \sqrt{\frac{L}{g}}$
When the length of the pendulum is halved, the new length $L'$ would be $\frac{L}{2}$. Thus, the new period $T_2$ can be calculates as :
$T_2=2\pi \sqrt{\frac{\frac{L}{2}}{g}}=2\pi \sqrt{\frac{L}{2g}}=2\pi \left(\frac{1}{\sqrt{2}}\right)\sqrt{\frac{L}{g}}=\frac{1}{\sqrt{2}}.2\pi \sqrt{\frac{L}{g}}=\frac{T_1}{\sqrt{2}}$
We are given that the new period $T_2$ is $\frac{x}{2}T_1$. Therefore, we can set up the equation :
$\frac{T_1}{\sqrt{2}}=\frac{x}{2}T_1$
To din the value of $x$, we solve for $x$ :
$\frac{1}{\sqrt{2}}=\frac{x}{2}$
Multiplying both sides by 2 :
$\frac{2}{\sqrt{2}}=x$
Simplify to :
$x= \sqrt{2}$
Hence, the correct answer is :
Option 2: $\sqrt{2}$