# Grade Eight Science Notes – Unit Three (Systems in Action)

## Self-explanatory.

Systems In Action   1

Intro Questions: 1

Law of Conversation of Energy: 1

Work: 1

Mechanical Advantage (MA): 1

Ideal Mechanical Advantage (IMA): 2

Follow-Up Questions: 2

Efficiency (E): 2

Friction: 3

Pulley Systems: 3

Levers: 3

Notes pg 132-137  3

IMA Shortcuts: 3

Gears: 4

Homework pg 143: 4

Jan 8/10

1.      What is a mechanical system? What are the functions of machines?

2.     What is a force? What types of forces of there? What is the measurement unit of force?

3.     What is work? How do we calculate work?

4.     What is energy? What forms of energy are there?

1.      A mechanical system is a group of physical parts that interact with each other and function as a whole in order to complete a task. The functions of machines are so that they make the “work load” less for people that use the machines. They will usually make the force needed to do a task less for the person operating the machine. There is an input and output force and increase a force, increasing the distance, or the direction of the force.

2.     A force is a push or pull that acts on an object and the measurement unit of force is Newtons. The different types of forces include contact forces, friction, gravity and action-at-a-distance forces.

3.     Work is defined as the amount of effort expended when a force causes an object to move a distance and energy is transferred. Work is usually how much energy is required to finish a task (move an object). Work = Force * Distance; work is measured in joules.

4.     Energy is the ability to do work and the forms of energy include kinetic energy, gravitational energy and potential energy.

Law of Conversation of Energy:

Energy can be neither created nor destroyed, but only changed from one form to another.

Work:

Is it possible to have no work done, but exert a force? Create a scenario where this is the case. (W = F * d)

Leaning on a wall would exert a force, but wouldn’t have any work done.