Difficulty: Easy
Correct Answer: False
Explanation:
Introduction / Context:
Pulleys are classic simple machines used to gain mechanical advantage. There are three traditional “systems of pulleys.” Each system has a distinct expression for velocity ratio (VR), which relates effort movement to load movement. Misremembering which VR belongs to which system is a common exam error.
Given Data / Assumptions:
Concept / Approach:
For the three classical systems: First system: VR = 2^n. Second system: VR = 2^n − 1. Third system: VR = n. The claim “VR = n” therefore pertains to the third system, not the second.
Step-by-Step Solution:
Identify the system: it is the second system. Recall standard formula: VR_second = 2^n − 1. Compare with claim VR = n ⇒ mismatch. Hence the statement is false.
Verification / Alternative check:
For n = 3: second system VR = 2^3 − 1 = 7. If one incorrectly used n, VR would be 3, which clearly contradicts textbook results and simple rope-segment counting.
Why Other Options Are Wrong:
“True”: incorrect; VR = n belongs to the third system. “True only if massless/frictionless”: VR formulas already assume ideal kinematics; friction affects efficiency, not VR. “True when n = 2”: still wrong; for n = 2, VR = 3 (not 2). “True for first system”: first system has 2^n, not n.
Common Pitfalls:
Mixing up the three systems’ formulas. Confusing velocity ratio (a kinematic quantity) with mechanical advantage (a force ratio affected by friction).
Final Answer:
False
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