Vectors
A vector is a quantity that has both magnitude (size) and direction.
Vectors are usually represented by arrows where the length of the arrows represent the size of the vector and show the direction it is acting in.
Vectors may act in directions that are:
- Parallel
- Anti - parallel ( parallel but in opposite directions)
- Angled to each other
Calculating Resultant Vectors
Parallel vectors
These are calculated by simple addition of all the vectors involved. The direction is the direct that they are all moving in.
These are calculated by simple addition of all the vectors involved. The direction is the direct that they are all moving in.
Anti Parallel vectors
The resultant magnitude of this is calculated by addition of all the vectors in one direction and subtraction of the vectors in the opposite direction. The direction follows the direction where the overall sum is larger.
The resultant magnitude of this is calculated by addition of all the vectors in one direction and subtraction of the vectors in the opposite direction. The direction follows the direction where the overall sum is larger.
Below are some examples of calculations of resultant vectors for parallel and anti parallel vector
Angled Vectors
Vectors can also act at angles to each other.
Vectors can also act at angles to each other.
Vectors that act at angles to each other may be calculated by use of the parallelogram law.
Parallelogram Law of Vector Addition states that when two vectors are represented by two adjacent sides of a parallelogram by direction and magnitude then the resultant of these vectors is represented in magnitude and direction by the diagonal of the parallelogram starting from the same point.
Students should be able to:
- Distinguish between scalars and vectors and give examples of each
- Use scale diagrams to find the resultant of two vectors
- Calculate the resultant of vectors which are parallel, anti-parallel and perpendicular
- Explain that a single vector is equivalent to two other vectors at right angles
Forces
A force is a push or pull. It can cause an object at rest to move or cause an object in motion to change speed, direction or come to a stop. A force can also cause an object to change its shape or size.
Mass and Inertia
Recall:
- Mass – The amount of matter in an object. Units: kilograms (kg)
- Inertia is the resistance of an object to a change in state of motion.
Weight
Weight is the force of gravity acting on an object. Units: Newtons (N)
Weight = mass x acceleration due to gravity
Weight = mass x acceleration due to gravity
Machines
We often think about machines as equipment in a factory:
Or electronic devices
Machines can however essentially be defined by three (3) simple characteristics:
- Makes a task easier
- All require an energy input of some kind
- All transfer energy
Are these devices therefore machine?
Do you think people used machines long ago?
Even before electronics and industries people have used "Simple Machines"
At this point we will focus on one of the most common of the simple machines: the Lever
Levers
A lever is a type of machine which uses a pivot or fulcrum to transfer the energy input of the effort to the load
There are three (3) types or classes of levers that are identified by the positions of the three main parts of the lever:
There are three (3) types or classes of levers that are identified by the positions of the three main parts of the lever:
- The pivot (fulcrum)
- The effort (input force)
- The load ( output force)
Levers and other machines can be grouped as either:
Force and Distance Multipliers in the Human Body
Question:
- Is all the used, or all the force applied to machines at the effort really transferred to the load?
Some energy always gets wasted as heat, usually because of friction between parts.
The energy of the effort must therefore:
1.Overcome Friction
2.Move the Load
How well a machine utilizes the energy input into it can be described as its Efficiency.
The energy of the effort must therefore:
1.Overcome Friction
2.Move the Load
How well a machine utilizes the energy input into it can be described as its Efficiency.
Efficiency
Efficiency is simply, the ratio of the output to the input of any system
Pressure
Recall: A force is a push or pull. It can cause an object at rest to move or cause an object in motion to change speed, direction or come to a stop. A force can also cause an object to change its shape or size.
The effect of a force however is not only dependent on the size of the force but also the area upon which it acts. This is called the Pressure.