Which insect is used to control the spread of prickly pear cactus $(Opuntia)$?

Magnetic lines of force due to a bar magnet do not intersect because

Two persons $A$ and $B$ are located in the $X-Y$ plane at the points $(0,0)$ and $(0,10)$ respectively. (The distances are measured in $MKS$ units). At time $t=0$,they start moving simultaneously with velocities $\overrightarrow{v}_A = 2\hat{j} \text{ m/s}$ and $\overrightarrow{v}_B = 2\hat{i} \text{ m/s}$ respectively. The time after which $A$ and $B$ are at their closest distance is

$A$ galvanometer,having a resistance of $50 \,\Omega$,gives a full-scale deflection for a current of $0.05 \,A$. The length in meters of a resistance wire of cross-sectional area $2.97 \times 10^{-2} \,cm^2$ that can be used to convert the galvanometer into an ammeter which can read a maximum of $5 \,A$ current is (Specific resistance of the wire = $5 \times 10^{-7} \,\Omega \cdot m$)

What does the given structural formula represent?

Two bodies of masses $0.1 \,kg$ and $0.4 \,kg$ move towards each other with the velocities $1 \,m/s$ and $0.1 \,m/s$ respectively. After collision,they stick together. In $10 \,s$,the combined mass travels .......... $m$.