JEE Main · 2004 · 24 Apr 2004 · Offline · Work, Power & Energy

A force

F = (5 \hat{i} + 3 \hat{j} + 2 \hat{k}) N

is applied over a particle which displaces it from its origin to the point

r = (2 \hat{i} - \hat{j}) m

. The work done on the particle in joules is

(A)-7
(B)+7✓ Correct
(C)+10
(D)+13

Answer: (B)

Solution

Work is the dot product of the force with the displacement. Starting from the origin and ending at

2 \hat{i} - \hat{j}

, the displacement is

s = 2 \hat{i} - \hat{j}

. Hence

W = (5 \hat{i} + 3 \hat{j} + 2 \hat{k}) \cdot (2 \hat{i} - \hat{j}) = 5 (2) + 3 (- 1) + 2 (0) = 10 - 3 = 7

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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