Physic problem

[TheRedViper]

Kinda off topic, but came across this problem in a physics book yesterday and I cant seem to get it out of my head since im a stubborn person.

 

I made an handwritten copy to avoid copyrights issues. It says a man doing the plank at a 12 degree angle is 182.88cm tall, weighting 80kg with a 35cm span from head to shoulders and 25cm shoes. They want the normal force applied to the hands and the one applied to the feet.

 

Basically, my initial logic was that; since his back is inclined 12 degrees, to just cos12 the gravitational gorce but then they want the normal on the hands and the feet. So I'm curious how you would proceed.

[Dash Lambda]

Just sum the torques!

.9144F-.5644H=0 -> F=(5644/9144)H

.35H-.9144(80g)+1.8288F=0 -> .35H-.9144(80g)+1.1288H

H≈485.106885 N, F≈299.425116 N

 

The trig didn't matter. (Yohohohoho!)

[spwath]

25 minutes ago, Dash Lambda said:

Just sum the torques!

.9144F-.5644H=0 -> F=(5644/9144)H

.35H-.9144(80g)+1.8288F=0 -> .35H-.9144(80g)+1.1288H

H≈485.106885 N, F≈299.425116 N

 

The trig didn't matter. (Yohohohoho!)

Yeah, was going to say that, need the torqueseses.