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

Asked by Nikson Panigrahi | 27th Feb, 2011, 12:00: AM

Expert Answer:

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

Answered by  | 27th Feb, 2011, 10:20: PM

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