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# notes2 - Chapter 2 Kinematics in 1D Mechanics the study of...

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Chapter 2: Kinematics in 1D Mechanics - the study of the motion of objects (atoms, blood flow, ice skaters, cars, planes, galaxies, …) - Kinematics - describes the motion of an object without reference to the cause of the motion - Dynamics - describes the effects that forces have on the motion of objects (Chapter 5) - [ Statics - describes the effects that forces have on an object which is at rest (bridge, building, ….)] y x A Kinematics provides answers to the questions: 1) Where is an object? 2) What is its velocity? 3) What is its acceleration? y’ x’

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Displacement Δ x = x f - x i = displacement [L] = 15 m - 5 m = 10 m in positive x-direction If x f =-5 m, then Δ x = -5 m - 5 m = -10 m in positive x-direction or (10 m in the negative x-direction) C = 44.6 m @ 38.4 °
Speed and Velocity Average speed = distance/(elapsed time)=D/ Δ t While average velocity is displacement/(elapsed time): v x , avg = x f x i t f t i = Δ x Δ t [L] [T] t = time (sec), time is a scalar v avg = x f - x i t f t i = Δ x Δ t in 1-(spatial) dimension. Or in vector notation: A vector with dimensions of [L]/[T], in S.I., units are m/s

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Simple Example A traveler arrives late at the airport at 1:08pm. Her plane is scheduled to depart at 1:22pm and the gate is 2.1 km away. What must be her minimum average running speed (in m/s) to make the flight? Solution Given: t i = 1:08 pm, t f = 1:22 pm, D = 2.1 km What is average speed v av ? Δ t = t f - t i = 1:22 - 1:08 = 14 mins v av = D/ Δ t = (2.1 km)/(14 mins) = 0.15 km/min = (0.15 km/min)(1000 m/1 km)(1 min/ 60 s) v av =2.5 m/s
Instantaneous Speed and Velocity Time Position x t i t f v x = lim Δ t 0 Δ x Δ t Instantaneous velocity

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notes2 - Chapter 2 Kinematics in 1D Mechanics the study of...

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