This week in class we started our new unit called Energy and Society, we started the unit talking about work and how we calculate work. I wanted to create a little note for you to summarize some key things you should know and remember.
W = ∑FΔd
WHAT TO REMEMBER?
- Work is being done only when a force displaces an object.
- The unit for work is Joules (J) named after James Joules.
- If a force is applied on an object, but the object does not move, there is no work being done (Physics 11 page 223).
- 90° motion equals no work, while the object may be displaced the object is not the one that is affected by the force, for example carrying a backpack on your back, while walking to class. While you are moving the bag would also be considered displacing from one place to another, but this force is not place on the bag. (Fig.5)
- When there is work, there is acceleration.
Mechanical work is calculated using the equation:
W = ∑F(cos θ ) Δd
If the forces acting on a object in a direction opposite of the object’s displacement, θ would equal 180° meaning that cos θ = -1. The equation W = ∑F ( cos θ ) Δd becomes W= ( ∑F Δd ) (-1) and the amount of work is a negative value.
I also have this video that is very informative and seems like it would help us throughout this unit. It has some information on what work is and “how work…works”, but there is also some extra information on energy and power, which we haven’t gone through yet or learnt, but I was looking ahead of the chapter and saw that we will be learning some of these terms and thought it would be helpful if we were all to have a general idea on what power and energy is all about! I hope that this video will help you during this chapter!