Question

a force F is applied on an object to displace it through distance s . for what angle between them the work done will be
(a) maximum
(b) positive
(c) negative
(d) zero​

Answer 1

Thus work done is said to be negative if angle(θ) between applied force (F) and the displacement (S) is an obtuse angle i.e., θ > 90°. Examples of negative work done : (i) When a body is made to slide over a surface, the work done by the frictional forces is negative

Answer 2

Answer:

a) When the angle between them is 0°

b) When the angle between them is acute i.e. more than 0° but less than 90°

c) When the angle between them is obtuse i.e. more than 90° but less than 180°

d) When the angle between them is 90°

Explanation:

Work done = Force x Displacement x Cosθ

where θ is the angle between the force and displacement

a) For maximum work done, cosθ must be maximum. So, the maximum value of cosθ is 1 when θ = 0°

b) For positive work done, cosθ must be positive. So, cosθ is positive for all acute angles. (0°<θ<90°)

c) For negative work done, cosθ must be negative. So cosθ is negative for all obtuse angles. (90°<θ<180°)

d) For zero work done, cosθ must be 0. So the value of cosθ is zero when θ = 90°

Hope it helps,

Alvika