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Velocity vs. Time. Analysis of a Velocity vs. Time graph. Velocity vs. Time Graphs. Constant velocity. Constant positive acceleration. Velocity vs.Time graphs. Constant negative acceleration but object has changed direction (WHY?). Constant negative acceleration. Slope of a V vs. T Graph.
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Velocity vs. Time Analysis of a Velocity vs. Time graph
Velocity vs. Time Graphs Constant velocity Constant positive acceleration
Velocity vs.Time graphs Constant negative acceleration but object has changed direction (WHY?) Constant negative acceleration
Slope of a V vs. T Graph Rise / Run On a velocity vs. time graph Rise = Δv = vf - vi Run = Δt = tf - ti Slope = Δv / Δt… Average Acceleration (aave)
Using slope to predict motion • On a velocity vs. time graph • If slope is 0, then acceleration is 0. The velocity is constant. • If slope is positive, acceleration is constant. • If slope is negative, acceleration is constant in the opposite direction.
Is the object changing speed? • You must consider both the direction of the velocity and the direction of the acceleration. • If velocity and acceleration are in the same direction object is speeding up. • If the velocity and acceleration are in opposite directions object is slowing down.
Speeding up v Is the velocity positive or negative? +v +a Is the acceleration positive or negative? t -a -v The sign for a and v are the same so both objects are speeding up!
Slowingdown (deceleration) v Is the velocity positive or negative? +v -a Is the acceleration positive or negative? t -v +a The sign for a and v are opposite so both objects are slowing down!
FindingDisplacement • Equal to the “area under the curve” on a v vs. t graph • Triangle A = ½ b×h • Rectangle A = l×w • Base and length are measured in s. • Height and width are measured in m/s. Area = (m/s)(s) = m
V (m/s) Area = l × w length = 3 s width = 50 m/s 50 Δd=150 m 3s ×50 m/s t (s) 1 2 3 4 5 6 7 -25
Velocity vs. Time Graphs • The slope of the line tells you the ____________ of the object. • The “area under the curve” represents the change in position or ____________of an object. displacement acceleration
Physics Book - Pg. 93 Practice Problems (13,15,16a) Section Review (1,2,4) Time to Practice