Describing Motion Words Drawings Graphs Equations

Distance or Displacement? Distance – how much ground the object has covered (what would the odometer say?) Distance = 12 m Displacement – how far out of place the object is (how far are you from home?) Displacement = 0 m

Ticker Tape Diagrams (a.k.a. Car with oil leak) Distance between dots represents the object's position change during that time interval Time interval is the same, but the distance traveled may change Why?

Water Drop Demo

Fast or Slow? A large distance between dots indicates that the object was moving fast during that time interval. A small distance between dots means the object was moving slowly during that time interval.

Speed vs. Velocity Speed: the rate of change of position, the rate at which an object moves. Velocity: the speed in a certain direction

Acceleration Acceleration: the rate of change of velocity. An object accelerates if its speed changes or if its direction changes For the examples in this ppt, we assume that there is no change in direction.

Constant Velocity or Acceleration? The same distance between dots means that the velocity is constant (not changing) A changing distance between dots means that the object is accelerating (changing velocity)

What’s happening with velocity and acceleration? 1). . . . . . . . . . . . . . . . 2). . . . . . . . . 3). . . . . . . . . . . . . 4). . . . . . . . . . . . . . .

Constant Velocity Constant Velocity – How do we know? Same distance between cars for each time interval How fast is the car going? v = d/t = 10 m / 1 s = 10 m/s

Constant Velocity / P-t Graph Now, let’s put the time data on the x-axis of an x-y graph and move the position data to the y-axis. Constant Velocity Line on position time graph is straight with a constant slope

Changing Velocity Consider a car moving right with a changing velocity. Is the velocity increasing or decreasing? Increasing Is the car accelerating? Yes Now, put the data on an x-y graph

Changing Velocity/ P-t Graph Increasing velocity Acceleration Line on the position time graph is curved The line is getting steeper (slope is increasing)

Slope of P-t Graph = Velocity Constant Velocity No acceleration Changing Velocity +Acceleration

Using Slope to Describe Motion

Calculating Velocity v = d/t (this can be rearranged d=vt, t=d/v) Since velocity = slope of P-t Graph, we can calculate velocity using: velocity = slope = rise = Δdistance run Δtime v = d/t (this can be rearranged d=vt, t=d/v) If a car goes 50 meters in 10 seconds, than v = 50 m/10 s = 5 m/s

Velocity Practice Problems A boy runs a 5 km race in 25 minutes. What is his velocity? A bird flew for 60 seconds at 3 m/s. How far did it fly? A car drove 200 km at 30 km/hour. How long was the car driving?

Velocity and Acceleration Constant velocity No Acceleration Acceleration = Slope of v-t graph = 0

Velocity and Acceleration Changing velocity Accelerating Acceleration = slope of v-t graph

Calculating Acceleration Since acceleration is the slope of the v-t Graph, we can calculate acceleration using: a = slope = rise = Δv = vf – vi run Δt t a = vf – vi where vf = final velocity t and vi = initial velocity and t = time

Calculating Acceleration

Comparing Velocity and Acceleration Constant Velocity Changing Velocity

Motion 3-2-1 Review 3 Things you learned about motion 2 Things you already knew about motion 1 Question you have about motion