4 A box of mass 2.5 kg is on a smooth horizontal table, as shown in Fig. 4. A light string AB is attached to the table at A and the box at B . AB is at an angle of \(50 ^ { \circ }\) to the vertical. Another light string is attached to the box at C ; this string is inclined at \(15 ^ { \circ }\) above the horizontal and the tension in it is 20 N . The box is in equilibrium.
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\caption{Fig. 4}
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- Calculate the horizontal component of the force exerted on the box by the string at C .
- Calculate the tension in the string AB .
- Calculate the normal reaction of the table on the box.
The string at C is replaced by one inclined at \(15 ^ { \circ }\) below the horizontal with the same tension of 20 N .
- Explain why this has no effect on the tension in string AB .