if the value of force calculated from the momentum equation

if the value of force calculated from the momentum equation is negative, what does it mean?

Solution

Momentum equation is:

Sum of all forces with respect to a coordiante axes = change in momentum (with respect to same coordinate axis)

So, if you assume a force to be applied in some specific direction and you obtain the force from the momentum equation as negative, this implies your assumed direction is wrong and you have to change the direction of the force on the system considered. Magnitude remains unaffected.