NECO 2002 Physics · Question 9

An object weighing 0.60N is hung on a spiral spring and caused it to extend by 6.0cm. The object is removed…

Question

An object weighing 0.60N is hung on a spiral spring and caused it to extend by 6.0cm. The object is removed and a black of wood replacing it causes the spring to extend by 10.0cm. What is the weight of the block of wood?

A.0.10N
B.0.36N
C.0.80N
D.1.00N
E.3.60N

Answer: D. 1.00N

Explanation written with AI and checked against the answer key

Analyze the question A spiral spring obeys Hooke's law. The extension is directly proportional to the load, provided the elastic limit is not exceeded. We are given one load and its extension, and a second extension for which we must find the load. Concept Hooke's law: F = ke, so F/e = k, which is constant for the same spring. Solution Find the spring constant from the first case: k = F/e = 0.60 N / 6.0 cm = 0.10 N/cm Use it for the wooden block, which extends the spring by 10.0 cm: F = ke = 0.10 N/cm × 10.0 cm = 1.00 N Check with a ratio: F₁/e₁ = F₂/e₂ 0.60/6.0 = F₂/10.0 F₂ = (0.60 × 10.0)/6.0 = 1.00 N The weight of the block of wood is 1.00 N. Tip When the same spring is used, set up the ratio F₁/e₁ = F₂/e₂. You don't need to convert units, since the units cancel as long as both extensions are in the same unit (here, cm). Always check that the answer is sensible: the extension is larger (10 cm > 6 cm), so the weight must be larger than 0.60 N, which rules out options A and B.

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