Final answer:
To determine the force at point x=15cm with k=10500N/m and work done W.D= -1/2kx², apply Hooke's Law (F=kx), yielding a force magnitude of 1575N.
Step-by-step explanation:
To find the magnitude of the force at point x=15cm, given the spring constant k=10500N/m and the work done by the force W.D= -1/2kx², we can use Hooke's Law, which states that the force exerted by a spring is directly proportional to the displacement and is given by F=kx. Substituting the given values, we get F=kx=10500N/m × 0.15m = 1575N. Hence, the magnitude of the force is 1575N.