1. Chapter 2—Motion in One Dimension Section 1: Displacement and Velocity

2. Distance—the total path-length traveled by an object; add-up each leg of the trip.  Units: meters, feet, km, cm, inches, miles, light-years  Symbol: d  Scalar Quantity—a quantity that has magnitude (size) only; no direction.  Examples: distance, speed, mass, density, time, energy

3. Example of Distance: A = 50 m B = 45 m C = 40 m A + B = 95 m

4. Displacement—the straight-line distance between two points, along with direction.  Units: SAME AS FOR DISTANCE  Symbol:  x  Vector Quantity—a quantity that has both magnitude and direction.  Examples: displacement, velocity, acceleration, force, momentum.

5. Example of Displacement: A = 50 m B = 45 m C = 40 m C = 40 m, north

6. Speed—the rate at which a distance is traveled. ◦ Units: m/s, mi/hr, km/hr, cm/s, ft/min, mi/day ◦ Symbol: s ◦ Scalar Quantity ◦ Instantaneous speed: an object’s rate of travel at a particular instant in time ◦ Average Speed—the total distance traveled divided by the total time of travel.

7. Example Problem: A car travels 120 km at 60km/hr. It then turns around and returns to its starting point at 30 km/hr. What was its average speed for the entire trip? d 1 = 120 kmd 2 = 120 km s 1 = 60 km/hrs 2 = 30 km/hr t 1 = d 1 /s 1 t 2 = d 2 /s 2 t 1 = 120 km/60 km/hrt 2 = 120 km/30 km/hr t 1 = 2 hrst 2 = 4 hrs s = d tot /t tot s = 240 km/6 hrs s = 40 km/hr You will absolutely, guaranteed, see a problem just like this one again on future tests!

8. Velocity—the rate of change in an object’s displacement ◦ Units: SAME AS FOR SPEED ◦ Symbol: v ◦ Vector Quantity ◦ Average Velocity—total displacement divided by total time of travel.

9. Note: If an object changes direction during its motion, its speed will be _______ the magnitude of its velocity. If an object does not change direction during its motion, its speed will be _______ the magnitude of its velocity. Can you explain why this is so?