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ERRATIC MOTION . Objectives: Determine position, velocity, and acceleration using graphs. APPLICATION. Having a v-s graph, can we determine a at s = 300m? How?. GRAPHING. -Better to handle complex motions difficult to describe with formulas. -Graphs provide a visual description of motion.
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ERRATIC MOTION Objectives: Determine position, velocity, and acceleration using graphs.
APPLICATION Having a v-s graph, can we determine a at s = 300m? How?
GRAPHING -Better to handle complex motions difficult to describe with formulas. -Graphs provide a visual description of motion. -Graphs are true meaning of dynamics
S-T GRAPH V-t: Find slope of s-t (v = ds/dt) at various points.
V-T GRAPH a-t: Find slope of v-t (a = dv/dt) at various points.
A-T GRAPH v-t is the area under the a-t curve. We need initial velocity of the particle.
s2 ½ (v1² – vo²) = ò a ds s1 A-S GRAPH Area under a-s curve= change in velocity (recall ∫a ds = ∫ v dv ). We need initial velocity
V-S GRAPH Knowing velocity v and the slope (dv/ds) at a point, acceleration is. a = v (dv/ds)
EXAMPLE Given: v-t graph for a train moving between two stations Find: a-t graph and s-t graph
a(m/s2) 4 3 t(s) -4 3 EXAMPLE (Solution:) a0-30 = dv/dt = 40/30 = 4/3 m/s2 a30-90 = 0 a90-120 = -4/3 m/s2
GROUP PROBLEMSOLVING Given: The v-t graph shown Find: The a-t graph, average speed, and distance traveled for the 30 s interval
GROUP PROBLEM SOLVING a(m/s²) t(s)
GROUPPROBLEM SOLVING (continued) Ds0-10 = ò v dt = = 400/3 m Ds10-30 = ò v dt = = s0-30 = = 1133.3 m vavg(0-30) = total distance / time =
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