When the mass m of a body moving through a force field is variable, Newton’s second law...

When the mass m of a body moving through a force field is variable, Newton’s second law takes on the form: If the net force acting on a body is not zero, then the net force F is equal to the time rate of change of momentum of the body. That is,

where mv is momentum. Use this formulation of Newton’s second law in Problems 21 and 22.

A uniform 10-foot-long chain is coiled loosely on the ground. As shown in FIGURE 1.3.18 one end of the chain is pulled vertically upward by means of constant force of 5 lb. The chain weighs 1 lb/ft. Determine a differential equation for the height x(t) of the end above ground level at time t. Assume that the positive direction is upward.