3.4.1.1 Scalars and Vectors Flashcards
What is a scalar quantity?
A scalar quantity is any physical quantity that is not directional.
It only has magnitude.
Give 6 examples of scalar quantities.
Mass Distance Speed Density Time Energy
What is a vector quantity?
A vector quantity is any physical quantity that has both magnitude and direction.
Give 6 examples of vector quantites.
Weight/Force Displacement Velocity Acceleration Momentum Impulse
How can a vector can be represented?
A vector can be represented by an arrow.
What does the length of the arrow represent of the vector?
The length of the arrow represents the magnitude of the vector.
What does the direction of the arrow represent?
The direction of the arrow represents the direction in which the vector acts.
How do you add two vectors together (using trigonometry)?
If two vectors are perpendicular to each other, you can calculate the size and angle of the resultant vector using trigonometry.
SOHCAHTOA and Pythagoras Theorem can both be used.
How could you find the resultant vector using scale diagrams?
You can find the resultant vector of two vectors by drawing a scale diagram of them, then measuring the length and the angle of the resultant vector on the diagram.
Which two scale diagram methods can be used?
The triangle of vectors.
The parallelogram of vectors.
Describe how the triangle of vectors method can be used.
1) Start by drawing a line which represents the vertical (north).
2) Then just measure the missing side with a ruler and the missing angle with a protractor.
Describe how the parallelogram of vectors method can be used.
1) Draw your scenario as a scale diagram.
2) Using a compass, draw a parallelogram, but complete with two dotted lines.
3) Join it up, corner to corner.
4) Measure the size of the resultant force based on your scale.
What two rules can be used when finding the resultant of vectors that act along the same line?
1) If the two vectors act in the same direction, you add the magnitudes of the vectors together and find the resultant vector.
2) If the two vectors act in opposite directions, you subtract the magnitudes of the vectors together and state the biased direction.
What is meant by ‘resolving a vector’?
Resolving vectors is the opposite of finding the resultant.
You start from the resultant vector and split it into two perpendicular components.
Which two components are there for a resultant force?
The components are normally horizontal and vertical.
How do you know which trigonometry equation to use by using the angle of the resultant force?
The component CLOSE to the angle = V x cos(-)
The component with a SPACE to the angle = V x sin(-)
CLOSE = COS SPACE = SIN
What diagram can be used to show the forces acting on an object?
A free-body force diagram can be used to show all the forces acting on an object.
What happens when all the forces acting on a body are balanced?
When all the forces acting on a body are balanced, the body is in equilibrium.
Describe an object in equilibrium.
If an object is in equilibrium, all the forces acting on it are balanced and therefore cancel each other out.
The resultant force on the object is zero.
When three forces act on an object, when is the object in equilibrium?
Their combined resultant is zero if the resultant of any of the two forces is equal and opposite to the third force.
Describe an object in equilibrium’s motion.
An object in equilibrium can be at rest of moving with constant velocity (constant speed and constant velocity).
