Speed and velocity

Objectives Terms Speed Velocity Describe one dimensional motion using equations for speed and velocity. Analyze one dimensional motion using equations for speed and velocity. Define and identify positive and negative velocities.

Equations 𝑉= 𝑑 𝑡 ____________________ is the distance traveled divided by the time taken. V __________________ d __________________ t ___________________ 𝑉 = ∆𝑥 ∆𝑡 ____________________ is the change in position divided by the change in time. V ___________________ ∆𝑥 change in ____________________ ∆𝑡 change in ________________

Rearranging Formulas Speed 𝑉= 𝑑 𝑡 Solve for distance Solve for time

Rearranging Formulas Velocity 𝑉 = ∆𝑥 ∆𝑡 Solve for change in position Solve for change in time 𝑉 = 𝑥 𝑓 − 𝑥 𝑖 ∆𝑡 Solve for initial position Solve for final position

Speed vs. Velocity Are speed & velocity just two different words for the same thing? In everyday life you probably use these words interchangeably. In Physics class, speed and velocity are related, but NOT exactly the same.

Using The Speed Equation A car travels 30 meters in a trip that lasts 2.0 seconds. What is the car’s speed? If you go a distance of 45 meters at a speed of 16 m/s, how long does this trip last? A fox runs at a speed of 9.7 m/s for 12 seconds. How far does the fox run?

How fast is fast? 0.1 m/s 1 m/s 10 m/s 100 m/s 1000 m/s See if you can come up with an example of when an actual object might move at each speed. 0.1 m/s 1 m/s 10 m/s 100 m/s 1000 m/s

Speed is scalar Distance is always ____________________. Time is always ____________________. Therefore, speed is always ____________________ ! So how do we tell the difference between moving backward and forward? We need a new variable: ____________________!

Velocity Velocity is defined as the ____________________ in ____________________ divided by the ____________________ in _______________. Reminder: Δ means“the ____________________.” A change in position, Δx, can be positive or negative. That means that velocity can be ____________________ or ____________________.

+ - + - Velocity & Direction ____________________ Velocity implies object is traveling: ____________________ or right/East ____________________ Velocity implies object is traveling: down/South or ____________________ + Left - Right Up Down North South - + West - East -

Velocity is a vector Velocity can have ____________________ or ____________________ values. The ____________________ of the velocity tells you the ____________________ of motion. Velocity is a ____________________. A vector is a type of variable which includes directional information in a mathematically useful way.

Using the Velocity Equation A car starts at 30m and finishes at 10m in a trip that takes 2.0 seconds. What is the change in position? What is the car’s velocity?

Using the Velocity Equation A car travels at 15m/s. Four seconds after starting out, it is at a position of 40m. What is the car’s change in position? Where did the car start from?

Finding Change in Position Quick reminders: 𝑥 stands for ____________________ Subscript “i” means “____________________” Subscript “f” means “____________________” Example: If a boy walks from a starting position of 3.2m to an ending position of 7.1, what is the boy’s change in position?

Finding Velocity If a boy walks from a starting position of 3.2m to an ending position of 7.1 in 2 seconds, what is his velocity?

Finding Velocity If a boy walks from a starting position of 7.1m to an ending position of 3.2m in 2 seconds, what is his velocity?

Positions & Velocities Part 1 Can there be a positive position and a negative velocity? - +

Positions & Velocities Part 2 Can there be a negative position and a positive velocity? - +

Positions & Velocities Part 3 Can there be a negative position and a negative velocity? - +

Positions & Velocities Part 4 Can there be a positive position and a positive velocity? - +

Assessment A swallow moves 80 meters east in 5 seconds. What is its speed? What is its velocity? How can the two be different?

Assessment Write an English sentence that means the same as this equation:

Assessment Give an example of an object with positive position and negative velocity.