Question

Q. In order to do work :
(1) Force must act at 180 degree angle to the direction of displacement.
(2) Force may not act along the same direction as is the displacement.
(3) Force must act along the direction of displacement.
(4) Force must act normal to the direction of displacement.


Answer with reason. Qualitative Answer needed.

Answer 1

$\fbox { \bold {ANSWER}}$

In order to do work.....

1 ). If the angle b/w force and displacement is 180 °, then it means that the direction of applied force is in opposite to the direction of the displacement.

So, W = f × s × cos theta

W = - fs [ one factor will be negative] [ cos 180 = - 1 ]

Work done will be negative.

2 ). If force may not act along the same direction of the displacement, then their directions will be opposite, and hence work done will be negative.

3 ). Possible. If force is acting in the direction of the displacement , then the work done will be positive.
Because the angle b/w them will be 0°.

W = fs cos theta

W = fs cos 0°

W = fs

Hence, work done is positive.

4 ). If force will act normal ( 90 °) to the direction of displacement , then no work will be done.

E. G.

W = fs cos 90 °

W = 0.

No work will be done.

Overall,

In order to do work,

( 3 ). $\underline {\bold { Force \: must \: act \: along \ : the \: direction \: of \: the \: displacement.}}$

Answer 2

Answer:

I don't know if you answering