Displacement

What’s your vector Victor?

Displacement ()• a vector quantity• a change in position• the length and direction from the start point to the end

point (straight line)

The difference between DISTANCE and DISPLACEMENT:

distance (d) – length of path travelled

displacement () – length of straight line from start to finish (including direction)

distance vs. displacement animation

What’s your vector Victor animation

A student travels 2 km [E] and then goes 5 km [W]. What is the displacement?

1 cm = 1 km (create a scale)

mathematically…

[E] = +ved1 = +2 kmd2 = -5 km

= + = 2 + (-5) = -3

\ The displacement is 3 km [W]

2 km [E]

5 km [W]

3 km [W]

(include compass heading)

(draw 1st vector)(draw 2nd vector)

(draw resultant vector)

Velocity

Velocity (• a vector quantity• rate of change of position• the displacement divided by the time interval

𝑣= �⃑�𝑡

A student rides her bike from her house to school. The path she takes is 2km long but the displacement is 1 km [E]. It takes her 30 minutes. Calculate her speed and velocity.

v =

=

= 4 km/h

𝑣= �⃑�𝑡

=

= 2 km/h [E]

speed velocity

Proper Form for Word Problems

G - given information (right hand margin)R - required information (right hand margin)A - appropriate formulaS - substituteS - solveS - statement (significant digits and units)

1. A cyclist travels 16.0 km [N] and then heads 24.0 km [S] in a time of 2.1 hours. Calculate her average velocity.

[N] = +ve

=16 km = -24 km

=

= 16 + (-24) = -8

= -8 kmt = 2.1 h = ? =

= - 3.8

\ the velocity of the cyclist was 3.8 km/h [S]

2. A person jogs at a speed of 3.2 m/s for 25 minutes. What distance did the person travel?

v = 3.2 m/s

t = 25 min. = 25 x 60 = 1500 s

d = ?

\ the distance travelled was 4800 m.

3. How much time will it take for a car to travel 2.3 km [W] at a velocity of 42.0 m/s[W]?

[W] = +ve

= 2.3 km = 2300m

= 42.0 m/s

t = ?

=

= 54.76

\the time was 55 s.

1.2 Prac. #5-9 UC #3-6