There are two ways you can get to the speed the soldier attained during the drop.
One way is to know that all stuff, light or heavy, drops at the same rate. Comedy now - get fixed in your mind the image of Galileo dropping rocks from the Leaning Tower of Pisa, even if its an urban myth! The soldier's 93 kg is not going to make any difference to how fast he arrives! You don't need Newton for this bit. You only need to understand what an
acceleration is.
Something dropped 1.5 metres. The acceleration was g metres per second per second. The extra "per second" is not a typo. We say "metres per second squared". There are simple equations to figure how long it takes to drop. A
time in seconds. Darn it though, you were given a
distance instead, but that's OK, because wherever you find some equations of motion, you find a simple one that let's you plug in the drop time and get at the velocity of soldier splat.
The "other" way is to say the potential energy m.g.h at the start will equal the kinetic energy (1/2)*m*v^2 when he arrives. You are after the 'v'. This is more direct, but I assure you it will not be enough to then figure the second part where the soldier is coming to a halt, involving
forces and
Mr. Newton.
OK, so Google is your friend, and Wiki knows all. Now go to
http://en.wikipedia.org/wiki/Equation_of_motion and look for "classic". Knowing that his initial velocity was zero helps, because the some equation terms become zero, leaving only an easy acceleration bit. Try and figure the velocity of arrival. Use that as the
initial velocity and apply the equations again, but in reverse - this time to get at the acceleration that brought him to a halt in 0.71 metres.
Getting the signs right is important here. If you arbitrarily choose downwards to be positive, then you will get a negative acceleration (a de-celeration?) that halts his motion. One of the numbers you need is his final velocity. (Yes - zero is a valid velocity!)
To come to a halt, he gets accelerated upwards, even though his slowing motion was downwards. Go after that value of acceleration.
Then, finally, invoke Newton. You know his mass. you figured the (de) acceleration. You can now figure the force on him.
If you need to, come back with the equations of motion you tried. Show us what you did. You will find that knowing the concepts allows you to not bother learning the equations by heart. Finding the force on the soldier requires you understand the concepts. We will help you all we can to get you there. The final answer is just arithmetic, and we expect you can use a calculator for that, and it takes only a minute or two. This is an expansive answer. Try not to let us down.
