AS Daily A Level Physics question
In a lab, a student uses two identical light springs, each marked 20 N m−1. They support the same 2.0 N weight in two set-ups: S = springs joined in series; P = springs in parallel sharing the load. What is the ratio of the total extension in S to that in P?
Answer
The correct answer is A.
Correct: A — 4:1. For two identical springs, the series arrangement has effective stiffness half of one spring (10 N m−1) and the parallel arrangement has double (40 N m−1); extension is inversely proportional to stiffness, so ratio = (2.0/10)/(2.0/40) = 4. A The series set-up extends four times as much as the parallel set-up because k_series = 10 N m−1 and k_parallel = 40 N m−1. B 2:1 underestimates the difference by assuming parallel behaves like a single spring rather than being twice as stiff. C 1:2 reverses the comparison, as if parallel extended more than series, which ignores that sharing the load makes the system stiffer. D 1:4 inverts the correct ratio, confusing which arrangement is stiffer.