• We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.

Physics again. only question i have left

M

MikeMike

Lifer
Tamar wants to cut down a large, dead poplar tree with her chain saw, but she does not want it to fall onto the nearby gazebo. Yoojin comes to help with a long rope. Yoojin, a physicist, suggests they tie the rope taut from the poplar to the oak tree and then pull sideways on the rope (the figure below ). If the rope is 40.0 m long and Yoojin pulls sideways at the midpoint of the rope with a force of 360.0 N, causing a 2.00-m sideways displacement of the rope at its midpoint, what force will the rope exert on the poplar tree? [Hint: Until the poplar is cut through enough to start falling, the rope is in equilibrium.]

my choices of answers are:
# 1660 N
# 1390 N
# 1530 N
# 1810 N

now what i have done is find the angle which the rope makes with the tree which is 5.7, however i then flipped my triangle around and used the angle of 84.289 and then did a sin of 84.289 = 360/H and found H. however that only gave me 361N and no where near the answers i could choose.

im trying to figure out what im doing wrong.

there is a picture with this issue, but idont know if i want to post it. im really confused as to what im doing wrong as is the answers im getting are no where near the answers possible.

please help?

im not asking for the answers just what im possibly doing wrong.

Image here
 
where is it pulling on the tree? where is the cut? surely the force would be a moment about the cutting point

ie find the y component of force, then times it by the perpendicular distance to the cut? reall not sure, icant really picture the scene with what you typed
 
Originally posted by: otispunkmeyer
where is it pulling on the tree? where is the cut? surely the force would be a moment about the cutting point

ie find the y component of force, then times it by the perpendicular distance to the cut? reall not sure, icant really picture the scene with what you typed
Click to expand...

one second on the pic.
 
Damn...it's an algebra word problem on steroids.

I work with a guy that could solve this problem in his head....in about two seconds.

He'd look right at you at say "The answer is (isert correct answer)...didn't you see that?"

Sadly, this is the same guy that can't quite differentiate b/t "Log Off" and "Shut Down."

I guess that's why they have lesser beings like me to work those probs. 🙁
 
Originally posted by: nourdmrolNMT1
Originally posted by: otispunkmeyer
where is it pulling on the tree? where is the cut? surely the force would be a moment about the cutting point

ie find the y component of force, then times it by the perpendicular distance to the cut? reall not sure, icant really picture the scene with what you typed
Click to expand...

one second on the pic.
Click to expand...


YGPM!
 
lol, I don't know the answer, but from cutting down trees, that's going to pull the bottom out once it goes through and once the bottom hits the ground to the right of the original stump, the top of the tree is going to be to the left of the center of gravity and it's going to crush the gazebo.
 
if assume forces on both trees equal, then vertical(oak) = vertical(dead) = 180

Foak = Fdead = 180/sin(theta) = 180/(2/(sqrt(2^2+20^2)) = 1808 = last choice
 
You must log in or register to reply here.

TRENDING THREADS

Back
Top