Homework Help: physics

Posted by sand on Saturday, November 12, 2011 at 6:05pm.

A steel beam (with linear mass density of 6.88 kg/m) has a total length of 10.0m and is suspended by two cables such that the beam hangs horizontally. Cable A is attached 1.00 m from the left end of the beam and cable B is attached 3.00 m from the right end of the beam. A 75.0 kg man is standing on the beam a distance of 2.5 m from the left end and a 3.5 kg cat is sitting, with a wry smile, 1.00 m from the right end of the beam. Assuming the cables are massless, what is the tension in Cable A?_________N What is the tension in cable B? _________N Some time later, after the man has kicked the cat off of the beam, the man is standing at the right edge of the beam. Should he be worried about the stability of this situation? explain.___________________________________________

physics - Damon, Saturday, November 12, 2011 at 7:18pm
In anticipation of part B I am going to take moments about the cable A attachment
I will do it all in Kg instead of Newtons because g will cancel except at the end.
m positive down
cable A x = 0 m = A
Man x = 1.5 m = 75
beam x = 4 m = 68.8
cable B x = 6 m = B
cat x = 8 m = 3.5

total m = 0 = A + B + 75 + 68.8 + 3.5
so
A + B = -147.3
now moments or torques about A
0 = 75*1.5+68.8*4+B*6+3.5*8
-6B = 415.7
B = - 69.3 Kg * 9.8 = 679 Newtons up tension
then
A -69.3 = -147.3
A = -78 * 9.8 = 764 Newtons up tension

Now with no cat and the man at the right
A + B = -143.8
0 =75*9 +68.8*4+B*6
B = -158.4
Oh my, that means that A will have to be positive (force down) to make the A+B=-143.3
The cable A will be under negative tension. Cables do not so well under negative tension, they collapse and the left end goes up and the man falls off.
physics - Anonymous, Sunday, October 21, 2012 at 10:26am
Could you explain the meaning of your symbols you use. for example the "m positive down" Ok i know what you mean, but this is extremely confusing if you don t state what each symbol means beforehand.
Cheers

Answer this Question

Related Questions

physics - 1.An elastic cord is 5.0m long and 1.0cm in diameter and acts as a ...
Physics - A 3.0m long uniform beam of mass 24kg hangs off the edge of a building...
Physics - A beam of mass mb = 10.0 kg, is suspended from the ceiling by a ...
Physics - A string with a length of 2.5m resonates in five loops. The string ...
Physics - A string with a length of 2.5m resonates in five loops. The string ...
Physics - A beam, B1, of mass M1 = 0.6887 kg and length L1=1 m is pivoted about ...
Physics - A beam of mass mb = 10.0 kg, is suspended from the ceiling by a single...
Physics - An 80kg construction worker sits down 2.0 meters from the end of a ...
physics - A light rigid bar is suspended horizontally from two vertical wires, ...
physics - A light rigid bar is suspended horizontally from two vertical wires, ...

For Further Reading

First Name:
School Subject:
Answer: