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lapo3399
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Problem: Spiderman (mass = 90kg) is swinging from his web. His center of mass is 10.0m off of the ground and his web has a length of 8.0m. It is connected to a pivot point that is the same height as his center of mass (so the web is held horizontal to the ground as he begins his swing). While holding the web during his swing, his center of mass is an additional meter from the end of the web.
a) What is the force on the web at the moment he reaches the bottom of his swing?
b) The web has a breaking limit of 3300N. Will the web snap and if so, how can he change his starting height to prevent this from happening?
Attempt:
a) m=90kg, r=8.0m + 1.0m = 9.0m
i.
Eg=mgh
=(90 kg)(9.8 m/s^2)(9.0m)
=7938 J
ii.
Ek=0.5mv^2
7938 J = 0.5(90 kg)v^2
v=13.2816 m/s
iii.
Fac = mv^2/r
= (90 kg)(13.2816 m/s)^2/(9.0 m)
=1764 N
iv.
Fg = mg
=(90 kg)(9.8 m/s^2)
=882 N
v.
Ft = Fg + Fac
=1764 N + 882 N
=2646 N
=2.6e3 N
Therefore the force on the web at the moment he reaches the bottom of his swing is 2646 N.
b) (Not really sure about my use of distance in this one; I used the radii of the circle and of the rope to find the force acting on the rope.)
i.
W=Fd
W=(2646 N)(9.0m)
W=23814 J
ii.
W=Fd
23814 J = F(8.0m)
F=2976.75 N
=3.0e3 N
Therefore the web will not break.
I'm not really confident that any of this is correct, so please provide insight if you can. Thanks!
a) What is the force on the web at the moment he reaches the bottom of his swing?
b) The web has a breaking limit of 3300N. Will the web snap and if so, how can he change his starting height to prevent this from happening?
Attempt:
a) m=90kg, r=8.0m + 1.0m = 9.0m
i.
Eg=mgh
=(90 kg)(9.8 m/s^2)(9.0m)
=7938 J
ii.
Ek=0.5mv^2
7938 J = 0.5(90 kg)v^2
v=13.2816 m/s
iii.
Fac = mv^2/r
= (90 kg)(13.2816 m/s)^2/(9.0 m)
=1764 N
iv.
Fg = mg
=(90 kg)(9.8 m/s^2)
=882 N
v.
Ft = Fg + Fac
=1764 N + 882 N
=2646 N
=2.6e3 N
Therefore the force on the web at the moment he reaches the bottom of his swing is 2646 N.
b) (Not really sure about my use of distance in this one; I used the radii of the circle and of the rope to find the force acting on the rope.)
i.
W=Fd
W=(2646 N)(9.0m)
W=23814 J
ii.
W=Fd
23814 J = F(8.0m)
F=2976.75 N
=3.0e3 N
Therefore the web will not break.
I'm not really confident that any of this is correct, so please provide insight if you can. Thanks!