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# A ball of mass 1 kg is at rest in position P by means of two light strings OP and RP. The string RP is now cut and the ball swing to position Q. If $\theta=45 ^{\circ}$ . Find the tension in the string OQ when RP is cut $(g=10 m/s^2)$

$(a)\;10 \sqrt 2 N\quad (b)\; 5 \sqrt 2 N \quad (c)\;2 \sqrt 2 N \quad(d)\;5 N$

When the ball reaches Q the ball is temperorily at rest but begins to move perpendicular to OQ
Therefore Net force along OQ=0
$T_2= mg cos \theta$
$T_2=1 \times 10 \large\frac{1}{\sqrt 2}$
$\quad=5 \sqrt 2 N$
Hence b is the correct answer.

edited Jan 26, 2014 by meena.p