Simple sum of forces parachute problem

[kirby27]

a 64 kg parachutist falling vertically at a speed of 6.3 m/s impacts the ground, which brings him to a complete stop in a distance of .92 m. assuming constant acceleration after his feet first touch, what is the average force exerted on the parachutist by the ground?

i know:
Vf=0
Vi=6.3
delta Y = .92

i used (Vfy)^2=(Viy)^2+2a(deltaY)

and found a = -21.57

i then used F=ma: F= (65)(-21.57)

and got -1402 N

is this right?

 

[SammyS]

Correct method.

Is the force exerted by the ground upward, or is it downward?

 

[kirby27]

i think the force exerted by the ground on the man is upward? should my answer be positive?

 

[SammyS]

I would think so.

 

[asteriatic]

I must first commend you for using the correct equations and units in your calculations. Your method seems sound and your answer of -1402 N is correct. However, it is important to note that the negative sign indicates that the force is acting in the opposite direction of the motion. In this case, the force is exerted by the ground on the parachutist to bring him to a complete stop. It is also important to consider any other factors that may affect the force, such as air resistance or the elasticity of the ground. Overall, your approach to solving the problem is correct and your answer is reasonable.