Motion Velocity & Acceleration

Speed vs. Velocity

Velocity Definition How far an object moves in a given amount of time AND the direction + velocity = displacement / time v = (d 2 – d 1 )/ t OR Δd / t OR d f - d i / t

Pulling It All Together Back to our ant explorer! Distance traveled: 7 cm Displacement: +3 cm Average speed: (7 cm) / (5 s) = 1.4 cm/s Average velocity: (+3 cm) / (5 s) = +0.6 cm/s cm s

Constant Velocity Lab

Acceleration

Change in Velocity You are at a stoplight and the light turns green so you step on the gas petal. How is the car’s speed changing? What happens to the speedometer? You come to a stop sign and apply the brakes. How is your speed changing? What happens to the speedometer? Acceleration- The rate of change of velocity.

A Change in velocity can be either: A change in speed OR A change in direction A merry-go round is running at a constant speed. What is happening to the velocity? Why? Is there acceleration? Why?

acceleration= final velocity- initial velocity time a = (v f – v i )units = m/s 2 t Acceleration Equation

A car traveling at 6 m/s slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is the car’s acceleration? = 0 m/s – 6m/s 6 seconds a = v f - v i time

A car traveling at 6 m/s accelerates to 9 m/s in 3 seconds. What is the car’s acceleration? a = v f - v i time

Positive acceleration Negative acceleration

Velocity Graphs 1.I have 2 lines representing movement plotted on a position graph. How can I tell which line is showing faster movement? 2.On a velocity line graph, how can I tell if the walker sped up? 3.On a velocity line graph I see a straight line that is flat – parallel to the bottom of the graph – what can I say about the walkers movement?