Growing crop plants in monoculture leads to ........

The half-life of $Ra^{226}$ is $1620$ years. Calculate the number of atoms that decay in one second in $1 \ g$ of radium (Avogadro number $= 6.023 \times 10^{23}$).

Which of the following is the main component of Portland cement (besides lime)?

Two bodies of mass $1\,kg$ and $3\,kg$ have position vectors $\hat{i} + 2\hat{j} + \hat{k}$ and $-3\hat{i} - 2\hat{j} + \hat{k}$,respectively. The centre of mass of this system has a position vector:

For the $RC$ circuit shown,the resistance is $R = 10.0 \ \Omega$,the capacitance is $C = 5.0 \ \mu F$ and the battery has voltage $\xi = 12 \ V$. The capacitor is initially uncharged when the switch $S$ is closed at time $t = 0$. At some time later,the current in the circuit is $0.50 \ A$. What is the magnitude of the charge across the capacitor at that moment in $\mu C$?

Diazo-coupling is useful to prepare some