3.4.1.1 Scalars and Vectors

Question 1

What is a scalar quantity?

Answer 1

A scalar quantity is any physical quantity that is not directional.
It only has magnitude.

Question 2

Give 6 examples of scalar quantities.

Answer 2

Mass
Distance
Speed
Density
Time
Energy

Question 3

What is a vector quantity?

Answer 3

A vector quantity is any physical quantity that has both magnitude and direction.

Question 4

Give 6 examples of vector quantites.

Answer 4

Weight/Force
Displacement
Velocity
Acceleration
Momentum
Impulse

Question 5

How can a vector can be represented?

Answer 5

A vector can be represented by an arrow.

Question 6

What does the length of the arrow represent of the vector?

Answer 6

The length of the arrow represents the magnitude of the vector.

Question 7

What does the direction of the arrow represent?

Answer 7

The direction of the arrow represents the direction in which the vector acts.

Question 8

How do you add two vectors together (using trigonometry)?

Answer 8

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.

Question 9

How could you find the resultant vector using scale diagrams?

Answer 9

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.

Question 10

Which two scale diagram methods can be used?

Answer 10

The triangle of vectors.

The parallelogram of vectors.

Question 11

Describe how the triangle of vectors method can be used.

Answer 11

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.

Question 12

Describe how the parallelogram of vectors method can be used.

Answer 12

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.

Question 13

What two rules can be used when finding the resultant of vectors that act along the same line?

Answer 13

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.

Question 14

What is meant by ‘resolving a vector’?

Answer 14

Resolving vectors is the opposite of finding the resultant.

You start from the resultant vector and split it into two perpendicular components.

Question 15

Which two components are there for a resultant force?

Answer 15

The components are normally horizontal and vertical.

Question 16

How do you know which trigonometry equation to use by using the angle of the resultant force?

Answer 16

The component CLOSE to the angle = V x cos(-)
The component with a SPACE to the angle = V x sin(-)

CLOSE = COS
SPACE = SIN

Question 17

What diagram can be used to show the forces acting on an object?

Answer 17

A free-body force diagram can be used to show all the forces acting on an object.

Question 18

What happens when all the forces acting on a body are balanced?

Answer 18

When all the forces acting on a body are balanced, the body is in equilibrium.

Question 19

Describe an object in equilibrium.

Answer 19

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.

Question 20

When three forces act on an object, when is the object in equilibrium?

Answer 20

Their combined resultant is zero if the resultant of any of the two forces is equal and opposite to the third force.

Question 21

Describe an object in equilibrium’s motion.

Answer 21

An object in equilibrium can be at rest of moving with constant velocity (constant speed and constant velocity).