Sun February 27, 2011 By: Nikson Panigrahi

What is cos (theta) in the formula of work done ? Please explain with example?

Expert Reply
Sun February 27, 2011
Dear student
Cos theta in the definition of work done is cos of the angle between force applied and the displacement.
For example, for a body freely falling under the effect of gravity,
F = mg
The direction of displacement & force is same, hence the angle between the two vectors is zero. So work done by gravitational force on freely falling body is W = mghcos0
For a ball thrown up against the gravity,
the force is acting downwards & the displacement is upwards.
So the angle between F and Displacement is 180
So work done by gravity on a ball moving up is W = mgh cos180
Home Work Help