Question

U
When a force vector F=(i+2j+k) N acts on
F=(i+2j+k) N acts on a body and produces a displacement of
S=(4i+j+7k)m, then the work done is
1) 9J
2) 13J
4) 1J
3) 5J
11​

Answer 1

Answer:

Option 2 is correct

Explanation:

Work done is dot product of displacement and force.

Given F=(i+2j+k) N

S=(4i+j+7k)m

W= F•S

W= (i+2j+k)•(4i+j+7k)

W= 4i•i+ 2j•j+ 7k•k

i•j=j•k=k•i=0

and i•i=j•j=k•k=1

therefore, W= 4+ 2+ 7= 13 J

Option 2 is correct