understanding sped and velocity

1. ESSENTIALi QUESTIONS
 Why are vectors more useful than
scalars?
 How is a velocity calculation different
than a speed calculation?

2. Vectors
 Quantities that have magnitude only, such as speed,
time, and mass, are called scalars.
 Quantities that require magnitude and direction to
completely describe them, such as velocity,
displacement, acceleration and force, are called
vectors.
 Vector can be represented graphically with arrow.
What’s your vector, Victor?
The tail The length of the arrow
represents the magnitude.
The longer the arrow,
the greater the magnitude.
The arrowhead or the tip
of the arrow represents
the direction.

3. Vector Addition
 Vectors can be added by placing them tip to tail.
 When vectors are added a resultant vector is determined by drawing
the resultant from the tail of the first vector to the tip of the last
vector.
 If vectors are in the same direction the process looks like this.
 If vectors are in opposite directions the process is seen below.
200 m/s 100 m/s
Resultant
300 m/s
200 m/s
100 m/s
Restultant
100 m/s

4. Distance vs. Displacement
 Distance ( ) is a length of a path between two points.
 Displacement ( ) is how far the object is from its starting point
and in what direction. Displacement is a vector quantity.
 To see the distinction between total distance and
displacement: imagine a person walking 70 m to the east and
then turning around and walking back (west) a distance of a 30
m. The total distance traveled is 100 m, but the displacement is
only 40 m east since the person is now only 40 m from the
starting point in east direction.
d

d

5. Velocity
 Velocity is Speed in a given direction.
 Changes in velocity:
1. Change in speed.
2. Change in direction.
3. Change in speed and direction.

6. Useful Formulas
 To calculate speed  To calculate velocity
t
d
s 
t
d
v


interval
time
distance

speed
interval
time
nt
displaceme

velocity