A long spanner is preferred over a short one to open a tight bolt because a long spanner:
AStores more potential energy
BProvides a larger lever arm for the same effort
CReduces friction at the bolt head
DIncreases the applied force at the bolt
Answer & Solution
Correct answer: B. Provides a larger lever arm for the same effort
1. Moment about the bolt equals force times the perpendicular distance from the bolt.
2. A longer spanner increases that perpendicular distance.
3. For the same applied effort, the turning moment becomes larger.
4. The bolt experiences a greater torque and is easier to rotate.
5. The spanner does not change the applied force itself; it changes the lever arm.
_Source: Selina Concise Physics ICSE Class 10, Ch 1 'Force' (icsehelp.com chapter extract)_
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