The work is marked with the letter A. It is calculated by multiplying the force F and the distance s. This applies to cases where the force and the path are parallel.
The unit of work is the joule. It is represented by the letter J. [N • m = J]
So, for example, if you are pulling a sledge with a force of 1 N through a distance 1 m, you would do 1 J of work.
In which cases the underlined objects do the work?
The jacket hangs on a hanger.
Katja liftsthe brush as she paints on the wall.
The hammer hits the head of the nail.
The mailman carries the package to the house.
The child pushes against the door so that the mother cannot open it.
The jacket hangs on a hanger. NO
Katja lifts the brush as she paints on the wall. YES
The hammer hits the head of the nail. YES
The mailman carries the package to the house. YES
The child pushes against the door so that the mother cannot open it. NO
Forces can act in different directions. Work is done only by a force acting parallel to the direction of motion of the body. A force acting perpendicular to the direction of motion does no work.
Watch the animation of Arphy pushing a shopping cart.
How much work does Arphy do while pushing the shopping cart from A to B?
For the calculation, you need information about the force that Arphy applied on the shopping cart FArphy and the distance s while Arphy travels from A to B.
A = FArphy • s
Arphy and his friend are moving the shopping cart. Watch the animation.
The work done is calculated as follows.
First, add the force of Arphy and the force of his friend. Multiply the sum of forces by the distance completed.
A = (FArphy+ Ffriend ) • s
There was a disagreement between Arphy and his friend, while pushing the shopping cart. They both applied the same force on the cart. Watch the animation.
Arphy and his friend pushed the shopping cart with equal force in opposite directions. Since the resultant of the forces that Arphy exerts on the shopping cart and the forces that his friend applied on the shopping cart are equal to 0, the shopping cart is at rest. The work has not been done.
missing TTS
A mother pushes a stroller in front of her with a force of 60 N in the direction of motion on a horizontal, rough floor. A frictional force of 15 N is applied on the stroller.
How much work does the mother do over a distance of 10 meters?
c) 600 J
What is the resultant force acting on the stroller when it is pushed?
a) 45 N
How much work is done by external forces on the stroller?
b) 450 J
Is the work done by a tractor pulling a baler greater if it presses hay bales in a shorter time? A baler is a machine for making hay bales.
c) The work is the same because it does not depend on time.
