A weightless spring is stretched 10 cm by a suspended 1-kg block. If two such springs are used to suspend the block, one spring above the other, to effectively provide one double-length spring, then the total stretch of the double-length spring will be
A)5 cm.
B)10 cm.
C)20 cm.
D)30 cm.
E)none of the above

Question

Quizplus · Accepted Answer

Each of the two springs will stretch 10 cm under the weight of the 1-kg block. When they are combined to form one double-length spring, the two springs will stretch together, resulting in a total stretch of 20 cm. This can be understood by considering that the weight of the block is distributed evenly across both springs, so each spring will stretch the same amount as if it were supporting only half the weight. Therefore, the total stretch of the double-length spring is twice the individual stretch of one spring, or 2 x 10 cm = 20 cm.

A Weightless Spring Is Stretched 10 Cm by a Suspended