Which of the following is a latex-based alkaloid?

For a cell,the terminal potential difference $(P.D.)$ is $2.2 \, V$ when the circuit is open and reduces to $1.8 \, V$ when the cell is connected to an external resistance of $R = 5 \, \Omega$. Determine the internal resistance of the cell $(r)$.

$A$ light string passing over a smooth light pulley connects two blocks of masses $m_1$ and $m_2$ (vertically). If the acceleration of the system is $g / 8$,then the ratio of the masses $m_1 : m_2$ is

$A$ compound contains $69.5\%$ oxygen and $30.5\%$ nitrogen and its molecular weight is $92$. The formula of that compound is

If $\cos ^{-1}\left(\frac{x^2-y^2}{x^2+y^2}\right)=k$ (a constant),then $\frac{d y}{d x}$ is equal to

$A$ simple harmonic oscillator consists of a particle of mass $m$ and an ideal spring with spring constant $k$. The particle oscillates with a time period $T$. The spring is cut into two equal parts. If one part oscillates with the same particle,the time period will be