(a) The work done in strecthing the spring is 122.5 N.
(b) The work done in compressing the spring is -122.5 N.
The work done in stretching a spring is positive since the applied force acts in the same direction as the displacement.
The work done in strecthing the spring is calculated as follows;
W = ¹/₂kx²
W = ¹/₂ x (5 x 10⁴) x (0.07)²
W = 122.5 N
The work done in compressing the spring is negative, since the applied force acts in opposite direction to the displacement of the spring.
The work done in compressing the spring is calculated as follows;
W = -¹/₂kx²
W = -¹/₂ x (5 x 10⁴) x (0.07)²
W = -122.5 N
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