When a mass is suspended from a spring and is in its equilibrium position, the upward force exerted by the spring is equal to the downward force of gravity acting on the mass.

Here's why:

* Equilibrium: Equilibrium means the net force on the mass is zero. The mass is not accelerating upwards or downwards.

* Forces at play:

* Gravity: The Earth pulls on the mass downwards with a force we call weight (mg, where m is the mass and g is the acceleration due to gravity).

* Spring Force: The spring pulls upwards on the mass. The force exerted by the spring is proportional to the amount the spring is stretched or compressed (Hooke's Law: F = -kx, where k is the spring constant and x is the displacement from equilibrium).

* Equilibrium Condition: For the mass to be in equilibrium, the upward spring force must exactly balance the downward gravitational force.

Let me know if you'd like to explore any of these concepts in more detail!