One end of a string of length l is connected to a particle of mass m and the other to a small peg on a smooth horizontal table. If the particle moves in a circle with speed v the net force on the particle (directed towards the center) is:

$$\begin{gathered} \left(1\right) T \\ \left(2\right) T-\frac{m{v}^2}{l} \\ \left(3\right) T+\frac{m{v}^2}{l} \\ \left(4\right) 0 \end{gathered}$$

A stone of mass 0.25 kg tied to the end of a string is whirled around in a circle of radius 1.5 m with a speed of 40 rev/min in a horizontal plane. The tension in the string is:

(1) 5.6 N

(2) 6.6 N

(3) 3.4 N

(4) 4.2 N