BELLWORK 9/10/15 HOW MANY SIG FIGS ARE IN THE FOLLOWING MEASUREMENTS? A) 0.0025 m B) 5.00g C)1250m D) 105g E) 3500m

Chapter 2-1 Displacement and Velocity

Point A --------> Point B Frame of Reference - In order to measure the distance of an object we must use a frame of reference. Point A --------> Point B - These are usually distinct points on the Earth's surface or distinguishing points in the sky.

Displacement is the shortest distance between the starting point and the ending point. A change in position Δ x = xf - xi

Turn to Page 41 in your books What is the gecko’s displacement in Figure 2?

Displacement vs. Distance If the gecko in Figure 2 traveled from the 24.5 cm mark to the 85.5 cm mark Displacement = 61.0 cm and Distance = 61.0cm BUT If the gecko traveled from the 24.5 cm to the 85.5 cm, and returned back to the 24.5 cm mark Displacement = 0 and Distance = 122.0 cm

Round trips If you return to the starting point (round trips) the displacement will always be = 0. Displacement is: How far away you are from where you started.

What is the runners Displacement? Distance?

Displacement can be + or (-) See Table 1 on Page 42 To the right , east, upward, or north = Positive To the left, west, downward, or south = Negative

Velocity is speed in a given direction

What is this Gazelle’s velocity?

Units **The SI units for measuring velocity is Meters/seconds **Velocity has to have a direction **Velocity can be either positive or negative (depending on the displacement value)

Units Displacement – SI unit for length is meters Time – SI Unit for time is seconds Speed (Velocity) – SI unit is m/s.

Vavg = Δx = xf – xi Δt = tf – ti

Speed vs. Velocity Velocity is a vector quantity that has a magnitude (numerical value) and a direction. Speed has no direction (scalar quantity)

Instantaneous Velocity The velocity at an instant of time

Classwork Page 44 #’s 1-6