Work is measured in Joules (J) In physics, work is done when an object is moved as a result of the action of a force. No work is done if the object does not move. Work is equal to the magnitude of the force times the magnitude of displacement. W = Fd Work is measured in Joules (J)

Work Work is done only when components of a force are parallel to a displacement. When the force on an object and it’s displacement are in different directions, only the component that is parallel to the object’s displacement does work. The other components do not do work.

Work Ex: If you push a crate along the ground and you are pushing completely horizontally, all of your effort (force) moves the crate. If you are pushing at an angle, only the horizontal component of your applied force causes displacement. When you push a grocery cart, you apply a force at a downward angle. Therefore, the work done is: W = Fd cos Θ

Work Ex: How much work is done on a vacuum cleaner pulled 3.0 m by a force of 50.0 N at an angle of 30.0° above the horizontal? G: F = 50.0 N d = 3.0 m Θ = 30.0° U: W E: W = Fd cosΘ S: W = (50.0 N)(3.0 m) (cos 30) S: W = 130 J

Work Work is a scalar quantity. Work can be negative. Work is positive when the component of force is in the same direction as the displacement. Work is negative when the component of force is in the opposite direction as the displacement. Negative work usually means the object is slowing down. You use the same equations for negative work.

Work If the net work on the object is positive, the object speeds up and work is done on the object. If the net work on the object is negative, the object slows down and work is done by the object on something else. Ex: The kinetic friction between a sliding box and the floor is opposite to the displacement of the box, so the work done by the force of friction on the box is negative.