A rigid uniform horizontal plank of mass m1 = 95 kg and length L = 7.4 m is supp
ID: 1313297 • Letter: A
Question
A rigid uniform horizontal plank of mass m1 = 95 kg and length L = 7.4 m is supported by two vertical strings as shown above.
String A is attached at a distance of d = 1.7 m from the left end of the bar and is connected to the ceiling.
String B is attached to the left end of the bar and is connected to the floor.
An object of mass m2 = 1870 kg is supported by the crane at a distance x = 6.4 m from the left end of the bar.
A/ Calculate the tension in string A.
B/ Calculate the tension in string B.
Explanation / Answer
Let tension in string A is Ta & in B is Tb.
Balancing moment about string B we have,
Ta*d = m1*g*(L/2) + m2*g*x
Putting values and solving
Ta = 71018.29 N.
Balancing moment about string A we have
Tb*d = m1*g*(L/2 - d) + m2*g*(x-d)
Putting values and solving
Tb = 51761.29 N.
Hence
a) Tension in string A = 71018.29 N.
b) Tension in string B = 51761.29 N.
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