4.1: Find the resultant of the following forces: 
(i) 10 N along x-axis 
(ii) 6 N along y-axis and 
(iii) 4 N along negative x-axis. 
Ans. (8.5 N making 45° with x-axis)


4.2: Find the perpendicular components of a force of 50 N making an angle of 30° with x axis. Ans. (43.3 N, 25 N)


4.3: Find the magnitude and direction of a force, if its x-component is 12 N and y- component is 5 N. Ans. (13 N making 22.6° with x-axis)


4.4: A force of 100 N is applied perpendicularly on a spanner at a distance of 10 cm from a nut. Find the torque produced by the force. Ans. (10 Nm)


4.5: A force is acting on a body making an angle of 30° with the horizontal. The horizontal component of the force is 20 N. Find the force. Ans. (23.1 N)



4.6: The steering of a car has a radius 16 cm. Find the torque produced by a couple of 50 N. Ans. (16 Nm)


4.7: A picture frame is hanging by two vertical strings. The tensions in the strings are 3.8 N and 4.4 N. Find the weight of the picture frame. Ans. (8.2 N)


4.8: Two blocks of masses 5 kg and 3 kg are suspended by the two strings as shown. Find the tension in each string. Ans.  (80 N, 30 N)

4.9: A nut has been tightened by a force of 200 N using 10 cm long spanner. What length of a spanner is required to loosen the same nut with 150 N force? Ans. (13.3 cm)


4.10: A block of mass 10 kg is suspended at a distance of 20 cm from the centre of a uniform bar 1 m long. What force is required to balance it at its centre of gravity by applying the force at the other end of the bar? Ans. (40 N)