Chapter 5 - Newton's Laws of Motion - Problems and Conceptual Exercises - Page 140: 8

(a) $F=414N$ (b) greater

(a) We know that $u^2=2as$ We plug in the known values to obtain: $u^2=2\times a\times 0.750m$ This simplifies to: $a=9.881m/s^2$ Now $F=mas$ $\implies F=(42Kg)(9.881m/s^2)$ $\implies F=414N$ (b) We know that the parachutist comes to rest in a shorter distance, therefore, the acceleration will be greater and consequently the force will also will be greater.