Physics Motion and Measurement 1262022 Objective Solve problems

Physics: Motion and Measurement 1/26/2022 Objective: Solve problems dealing with the position and/or velocity of an object

How do we describe how fast an object is moving? �Speed is defined as the rate at which something moves, or how far it moves in a given amount of time �As an equation, v = d/t (speed = distance / time) Distance = 5 cm Time = 2 sec Speed = 5 cm / 2 sec Speed = 2. 5 cm/sec

Scalar or Vector? �Speed is a scalar. It’s a number without a direction. �Just like distance (scalar) has displacement (vector), speed also has a vector equivalent, velocity. �Velocity ( v ) consists of both a speed and a direction �v = Δd/Δt ( velocity = displacement / change in time) �We can expand this out to v = (df - di)/(tf - ti)

Velocity and graphing Position vs. Time Position (m) �Think back to your position vs. time graphs �v = (df - di)/(tf - ti) �Compare that to the equation for slope of a line: m = (y 2 - y 1)/(x 2 - x 1) �Velocity is the slope of our position vs. time graph 12 10 8 6 4 2 0 0 2 Time (s) 4 6

Slope Position (m) �Remember, slope is “rise over run” or Δy/Δx �If we start with a position -time graph, we can figure out the velocity just by finding the slope Position vs. Time 12 10 8 6 4 2 0 0 Rise: 4 m Run: 2 sec 2 Time (s) 4 6 Slope: 4 m/2 sec Velocity = +2 m/s

Slope and Velocity �A steeper slope (on a Position-Time graph) means a higher velocity �A negative slope means a velocity in the negative direction

Practice �With a partner, do problems 25 -28 on p. 45 (skip the motion diagram in #28)