Newton’s second law says the net force on an object equals its mass times its acceleration. The word doing the work is net: it is the vector sum of every force acting, not any single one of them.
A car pushed forward by 6 kN of drive force while 2 kN of drag and friction push back accelerates under 4 kN, not 6. This is why a vehicle stops accelerating at top speed even though the engine is still producing force — drag has grown until the net force is zero.
Mass and weight are different things
Mass is how much matter there is, measured in kilograms, and it does not change with location. Weight is the gravitational force on that mass, measured in newtons, and it does. A 70 kg person weighs about 687 N on Earth and 113 N on the Moon, but their mass is 70 kg in both places — and so is the force needed to accelerate them sideways.
Impulse and the reason airbags work
The law can be rewritten as F = Δp / Δt, force is the rate of change of momentum. A collision changes momentum by a fixed amount regardless of how it happens, so stretching the time over which that change occurs reduces the peak force proportionally. Crumple zones, airbags, running shoes and gymnastic landing mats all exploit exactly this.