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May 18, 2015
2. 6-2 Distance & Displacement
Identify appropriate SI units for measuring distances.
Distinguish between distance and displacement.
Calculate displacement using vector addition.
3. Measure Distance
Distance is the measure of length of any path between two points.
The path can be a straight line.
Use the unit best suited for the distance:
Very large distance km
Mississippi River is 3780 km long.
Very small distance cm or mm
The distance a marble rolls on carpet 6 cm
Distances in betweencould be hm, dkm, m, or dm.
d1 , d2
x , y , or r displacement
xi , xf , yi, andyf
5. Vector vs. Scalar
Any quantity thathas magnitude (size), units, and direction
Any quantity that has only magnitude (size), and units, but direction does not matter.
6. Distance vs. Displacement
Distance is the length of any path between two points.
d = |x1| + |x2|
Displacement is the direction and straight line distance between starting point and finishing point.
x = x1+ x2
y = y1+ y2
For right triangles
r = ( x2 + y2)
Sign & direction are important!!!
A football player runs 25 meters up-field and is pushed back 3 meters when he is tackled. What is the players distance traveled and displacement?
A pitcher throws a baseball 20 meters to the catcher and the catcher throws the ball back to the pitcher. What is the distance traveled and the displacement of the ball?
The Lone Ranger runs 5 meters east to get away from the bad guys, but he stops when he sees more bad guys and runs 12 meters west to hide behind a rock. What was his displacement and total distance traveled?
10. 6-2 Summary
What is the difference between distance and displacement?
How do you find displacement?
When do you use Pythagorean theorem?