Per NCERT, while exercising, a girl lifts a dumbbell UP and then slowly lowers it DOWN. When does she do POSITIVE work on the dumbbell?
AWhen she lifts it UP (force and displacement both upward)
BShe never does positive work
COnly when she holds it still
DWhen she lowers it DOWN
Answer & Solution
Correct answer: A. When she lifts it UP (force and displacement both upward)
Per NCERT Example 7.1, lifting up = positive work (force and displacement aligned). Lowering = negative work (force up, displacement down).
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