Question

F is equal to i-2j position vectore is equal to (-j+k) find the moment of F about the origin​

Answer 1

Answer:

Correct option is

A

2

r

ˉ

=2i−j

F

ˉ

=2i+j−k

Hence moment of force about origin is

=

F

ˉ

×

r

ˉ

=(2i+j−k)×(2i−j)

=−i−2j−4k

And the work done

=

F

ˉ

.(r

2

−r

1

)

=(2i+j−k).(2i+j−(2i−j))

=(2i+j−k).(2j)

=2 joules

Explanation:

follow

Answer 2

Answer:

Correct option is

A

2

r

ˉ

=2i−j

F

ˉ

=2i+j−k

Hence moment of force about origin is

=

F

ˉ

×

r

ˉ

=(2i+j−k)×(2i−j)

=−i−2j−4k

And the work done

=

F

ˉ

.(r

2

−r

1

)

=(2i+j−k).(2i+j−(2i−j))

=(2i+j−k).(2j)

=2 joules