Introduction to Work


Work: whenever a force acts through a distance, work is done in a way that can be measured or predicted.
Work is defined as the product of force and the distance through which the force moves an object in its direction.
Work depends on two elements: force and distance. For a constant force and a straight line motion, work is expressed as:
work = w = F×d
Work is a scalar quantity (magnitude with no direction) and is measured in joules (J).

1 joule = (1 newton) × (1 meter) = 1 N • m
For example, when a ball is thrown by the baseball players (pitchers),
the work done on the ball as it falls is equal to the weight of the ball (force) times the distance.
Basically, even if a considerable force F is exerted but distance is zero then the work accomplished is zero!


The impulse is found using the Newton's second law F = m×a = m × Δv /t and if both sides are multiplied by t we obtain F ×t = m × Δv
We obtain the impulse and its unit is N•s.


Example 1

When lifting a box there is work being done but carrying it in the physics sense. Why?
Answer: When you a list a box, there was actually a force F exerted on the box and a distance from the ground until a body position.
However, carrying the box only without a movement then the work = 0.

Example 2

When you kick a ball, you do work on the ball (see picture below):
kicking a ball

Impact of Parallel Forces on Work



Exercise on Work

Check your answers here: Solution to the Work Exercise

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Date of last modification: Summer , 2019