# What constant force does the floor exert

• HJ^2
In summary: I'm guessing here, but I'd say it's a few Newton.(*) I'm not sure if " (*) " is supposed to be a footnote or something, but it doesn't seem to be doing anything.
haruspex said:
Right. The only unknown there is Fn. Solve.
Fn = (m*a) - Fg

With variables is;

Fn = (74.4 * 6.8411) - 9.8 = 499.177 ?

HJ^2 said:
Fn = (m*a) - Fg

With variables is;

Fn = (74.4 * 6.8411) - 9.8 = 499.177 ?
Fg is not 9.8 For one thing, it will be negative (since you have chosen up as positive).

haruspex said:
Fg is not 9.8 For one thing, it will be negative (since you have chosen up as positive).

Fgrav = -9.8*74.4?
If that's right, then;
Fn = (74.4*6.8411) - (-729.12) = 1238.10

HJ^2 said:
Fgrav = -9.8*74.4?
If that's right, then;
Fn = (74.4*6.8411) - (-729.12) = 1238.10
Right (but shared across two feet).
So, do you see where your prof went wrong?

haruspex said:
Right (but shared across two feet).
So, do you see where your prof went wrong?
Absolutely. I'll have to bring it up to her as I'm sure my class mates had similar concerns.

HJ^2 said:
Absolutely. I'll have to bring it up to her as I'm sure my class mates had similar concerns.
Good.
On a side note, if you calculate how far the athlete's mass centre must travel after touch down and before coming to rest, it's about 3m!

haruspex said:
Good.
On a side note, if you calculate how far the athlete's mass centre must travel after touch down and before coming to rest, it's about 3m!
Oh thanks! And thank you so much for your help + everyone else in this thread :)

• Introductory Physics Homework Help
Replies
7
Views
7K
• Introductory Physics Homework Help
Replies
38
Views
3K
• Introductory Physics Homework Help
Replies
7
Views
1K
• Introductory Physics Homework Help
Replies
43
Views
3K
• Introductory Physics Homework Help
Replies
2
Views
13K
• Introductory Physics Homework Help
Replies
1
Views
7K
• Introductory Physics Homework Help
Replies
2
Views
6K
• Introductory Physics Homework Help
Replies
3
Views
2K
• Introductory Physics Homework Help
Replies
9
Views
6K
• Introductory Physics Homework Help
Replies
1
Views
7K