The work done by a constant force F on a body that undergoes displacement d (both vectors) is:
AW = F · d (scalar product)
BW = F × d (vector product)
CW = F + d
DW = |F| |d|
Answer & Solution
Correct answer: A. W = F · d (scalar product)
1. Work is defined as the scalar (dot) product of force and displacement.
2. W = F·d = |F| |d| cosθ, where θ is the angle between F and d.
3. The cross product F × d gives a vector — that is the torque, not work.
4. |F| |d| is only correct when θ = 0.
_Source: NCERT Class 11 Physics Ch 5 "Work, Energy and Power", §5.2 Notion of Work, p. 76_
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