Passage IV
A student studied the properties of spring systems using weights and 3 identical, low-mass springs.
Study 1
The student suspended 1 spring from a support and measured the length of the spring. He attached a 10 N ( newton) weight to the spring and again measured the length of the spring (see Figure 1).
The student calculated the amount the spring was stretched by the weight He repeated the measurement using ocher weights. The results are shown in Table 1.
The spring constant, K. is the amount of force that must be exerted to stretch a spring a given amount. Based on Table 1, K for this spring was 100 N/m.
Study 2
The student suspended 2 of the springs in series (end to end ) from the support and measured their amount of stretch with various weights attached. He repeated the procedure with 3 springs in series (see Figure 2).
The results are shown in Table 2.
For 2 springs in series, K was 50 N/m: for 3 springs in series, K was 33 N/m.
Study3
The student suspended 2 of the springs in parallel (see Figure 3).
The student measured the amount or stretch with various weights attached. He repented the procedure with 3 springs in parallel. The results are shown in Table 3.
For 2 springs in parallel, K was 200 N/ m; for 3 spring in parallel, K was 300 N/m.
17. The student connected 2 of the springs in parallel to each other and attached them to hooks screwed into the wall. The student pulled horizontally on the springs, as shown in the figure below.
Based on Study 3, to stretch each spring 0.15 m, the student had to exert how much force?
Your Answer is
Correct Answer is D
Explanation
Look at the last row of table 3. When there are 2 springs in parallel, a force of 30 N is required to stretch 0.15 m