Question

The work done when a force of [F=(2i + 3j – 5k)] unit acting on a body produces a displacement [S=(2i + 4j + 3k)] unit is

(a) 30 unit
(b) 2 unit
(c) 1 unit
(d) Zero
​

Answer 1

Explanation:

Let us first try to Understand when work is said to be done.

By defination,"Work is said to be done if a body has some net displacement in the direction of applied force."

so, work done=component of force in the direction of displacement X displacement.

Therefore,W=(Fcosϴ X d)=F.d

By dot product rule,i.i=j.j=k.k=1 and i.j=j.k=k.i=0

F.d = (2)(1) +(3)(2) + (1)(-4)

=2 +6 -4 =4

Therefore,required work done is 4