This is College Physics Answers with Shaun Dychko. This rocket's lid is going to be decelerated at 196 meters per second squared and its mass is 2,100 kilograms. The question is what force needs to be applied to cause this deceleration. This force is the only horizontal force, so that makes it the net force. We have a formula for net force, it is mass times acceleration, that's Newton's second law. We can substitute little f in place of <i>F net</i>. That's what we do here. We say it equals mass times acceleration 2,100 kilograms times 196 meters per second squared requires a force 4.1 times 10 to the 5 Newtons.