11.1 DISTANCE ANDDISPLACEMENTAll of science is concerned with motion.The motion of objects change when forces actupon them.All objects have motion they just appear to bemotionless. All of matter contains atoms that arecontinuously in motion (vibrate and collide).In order to describe motion you must state thedirection in which the object is moving and howfast the object is moving.
*You have to choose a frame of reference. ( Todescribe motion accurately) It is a system of objects that are not moving withrespect to one another.EX. People on the bus are not a good frame ofreference because they are moving with the bus.You need to choose and object not moving outsidethe bus.You have to choose an appropriate frame ofreference to describe motion in a clear andrelevant manner.Relevant Motion is movement in relation to aframe of reference.
MEASURING DISTANCEDistance is the length of a path betweentwo points.SI unit for distance is the meter (m)However, for larger distances it is betterto use kilometers (km)
MEASURING DISPLACEMENTSDisplacement is the direction from the startingpoint and the length of a straight line from thestarting point to the ending point.Displacement use vectorsA vector is a quantity that has magnitude anddirection.Magnitude can be the size, length, or amount ofsomething.Arrows on maps represent vectors.Symbol for vector →
COMBINING DISPLACEMENTSDistance: Displacements along a straight lineUse vector addition or subtraction.Going 10 km east and 3 km west = 10-3 = 7Page 330 demoUse vector addition if in a straight line 4km +2km = 6km
DISPLACEMENT THAT ISN’T ALONG ASTRAIGHT PATHResultant vector- is the vector sum oftwo or more vectors.The vector goes directly from thestarting point to the end point.P. 331 Figure 4
SECTION 11.2 SPEEDAND VELOCITYSpeed- is the ratio of the distance an object movesto the amount of time the object moves.SI unit = m/s *use the units that make the mostsense. cars = miles/hr or km/hr2 Ways to express the speed of an object1. Average speed- (v) is the total distance traveled,(d) divided by the time, (t) it takes to travel thatdistance.
CALCULATING SPEEDFormula:Average speed = Total distance v=d Total time tSometimes you have to rearrange the formula tosolve for distance or time.d=v×t t=d v• The speed of the object can change during the time it moves but, this equation gives you the overall average.