how many newtons of tension are exerted in the strand?

Question

When a 100-N bag of nails hangs motionless from a single vertical strand of rope, how many newtons of tension are exerted in the strand?

How about if the bag is supported by four vertical strands?

Answer 1

a. 100 Newtons

b. 25 Newtons each, assuming uniform loading. Otherwise it is indeterminate.

Answer 2

First of all, draw a free-body diagram. Hanging motionless means that we have a system that is in equilibrium, therefore net force is zero. The downward force of gravity (also called weight) must equal the upward force caused by the string (called tension) in order for net force on the object to be zero. So with one strand:

Weight = tension
100 N = tension

Now we have four strands so,

Weight = T1 + T2 + T3 + T4 = 100 N

The four strands combined have a total tension of 100 N. If we assume that this tension is uniformly distributed, each strand exert 25 N of tension.