**1. The problem statement, all variables and given/known data**

A ring is moving on a vertical rod attached to a spring. Find the velocity of the ring when spring becomes horizontal. The spring is ideal with spring constant 400N/m. Mass of ring is 10kg. Natural length of spring is 4m. Initially the ring is at rest as shown in figure.(attachment)

**2. Relevant equations**

**3. The attempt at a solution**

I want to solve the problem using Newtons laws and not by conservation of energy method. I have no idea on where should I start. I have made the following equation:

Fcosθ + mg = ma ……..where F is the force by the spring

…….. θ is the angle between spring and rod

…….. a is the acceleration of the ring

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