The mass is just sitting there motionless. There is no acceleration and it is in equilibrium. What does this mean? This means that the net force in the y-direction (vertical direction) must be zero. I ...

SAE Transactions, Vol. 115, SECTION 7: JOURNAL OF PASSENGER CARS: ELECTRONIC AND ELECTRICAL SYSTEMS (2006), pp. 1046-1056 (11 pages) This paper presents an empirical dynamic model of a single spring ...