To determine the total work input, we can use the work formula, which states that work is equal to force multiplied by distance. In this scenario, the constant force applied is 70 pounds, and the distance over which this force is applied is 12 feet.
Calculating the work involves simply multiplying the force by the distance:
[ \text{Work} = \text{Force} \times \text{Distance} ]
[ \text{Work} = 70 , \text{lbs} \times 12 , \text{ft} = 840 , \text{foot pounds} ]
Therefore, the total work input to move the mobile hoist over the specified distance with the given constant force is 840 foot pounds. This computation directly aligns with the answer provided, confirming its accuracy within the context of this physics principle concerning work and energy.