Question

4. Explain positive , negative and zero work in the following fig.
​

Answer 1

Answer:

Explanation:

W = force×displacement×cosθ

case 1.

force and displacement in the same direction so the angle is zero and cos0 is one.

w = force×displacement

work is positive in this case.

case 2.

displacement is zero here.

so work = 0

case 3.

the angle between force and displacement is 180

w = - force×displacement

Answer 2

Concept:-

Work Done = F× s× cos(alpha)

where, F = Force applied

s= Displacement

alpha = angle between F and s

Solution:-

For (a) :-

Here, F and s are on same direction,i.e.,alpha is equal to 0°

Work Done = F×s×cos 0° = F×s = +ve work

For (b) :-

Here, F and s are perpendicular and also s is given to be 0

Work Done = F×s×cos 90° = 0

For (c):-

Here,F and s are in opposite directions,i.e

alpha = 180°

Work Done = F×s× cos 180° = -F×s = -ve work