1. Scalars and vectors

2. Which of the following is the odd one out?
Mass
Speed
Force
Temperature
Distance
Elephant

3. Which of the following is the odd one out?
Mass
Speed
Force
Temperature
Distance
Elephant

4. Scalars Scalar quantities have a magnitude (size) only. For example:
Temperature, mass, distance, speed, energy.
1 kg

5. Vectors Vector quantities have a magnitude (size) and direction.
For example:
Force, acceleration, displacement, velocity, momentum.
10 N

6. Scalars and Vectors vectors scalars No direction Magnitude (size)
Magnitude and direction
temperature
mass
velocity
force
acceleration
speed

7. Scalars and Vectors vectors scalars No direction Magnitude (size)
Magnitude and direction
temperature
mass
velocity
force
acceleration
speed

8. Representing vectors
Vectors can be represented by arrows. The length of the arrow indicates the magnitude, and the direction the direction!

9. Adding vectors
When adding vectors (such as force or velocity) , it is important to remember they are vectors and their direction needs to be taken into account.
The result of adding two vectors is called the resultant.

10. Adding vectors For example; Resultant force 2 N 6 N 4 N 4 m/s 5.7 m/s
Resultant velocity

11. Adding vectors
For example;
Resultant force
2 N
6 N
4 N

12. An interesting example
Think of a dog orbiting the earth with constant speed (in a circle).

13. An interesting example
At this point, what is its velocity?
velocity?

14. An interesting example
velocity

15. An interesting example
What is its velocity here?
velocity?

16. An interesting example
As you can see the velocity has changed as it is now going in another direction.
velocity

17. An interesting example
We have constant speed but changing velocity.
Of course a changing velocity means it must be accelerating! We’ll come back to this in year 12!
velocity

18. Question
Suppose you lay 3 metre rulers on the floor end-to-end to represent 3 vectors of equal magnitude. How could you produce a final vector of
A) the largest magnitude
B) the smallest magnitude
C) a magnitude of the length of 1 ruler

19. A) end to end = 3m
B) in a triangle = 0m
C) on top of each other, or 2 end to end with another on top

20. Flying in a side wind
A bird flies at a steady speed of 3 m s–1 through the air. It is pointing in the direction due north. However, there is a wind blowing from west to east at a speed of 2 ms–1.
1. What is the velocity of the bird relative to the ground?
2. What is the displacement of the bird, relative to its starting point, after it has flown for20 seconds? 
3. In what direction should the bird point if it is to travel in a northerly direction?