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A force ⃗F=(5̂i+3̂j+2̂k) N is applied over a particle which displaces it from its origin to the point ⃗r=(2̂i-̂j) m. The work done on the particle in joule is
Asked in AIEEE 2004 · Work from force and displacement vectors
- (1) -7
- (2) +7
- (3) +10
- (4) +13
Answer: (2) +7
Step-by-step solution
W=⃗F·⃗r=5×2+3×(-1)+2×0.
W=10-3=7 J.
Why the other options are wrong
- (1) Comes from reversing the direction of the displacement.
- (3) Comes from dropping the ̂j term of the dot product.
- (4) Comes from ignoring the minus sign on the y-displacement and adding 10+3.
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