BELLWORK 10/11/17 NB: Write “IN” and today’s date. Answer the following in complete sentence(s): What does acceleration mean to you? What 2 factors does velocity include? Speed and direction! In science acceleration can be applied to both increases and decreases in speed. Acceleration is the rate of change in velocity.

https://www.youtube.com/watch?v=eSLkJEjnFHQ

“Through” Calculating Average Acceleration The formula for calculating average acceleration is: Acceleration (a) = final velocity (vf) – initial velocity (vi) time (sec) Standard Units of acceleration: Meters per second per second m/s/s OR m/s2 Velocity is measured in meters per second and time is measured in seconds. So, acceleration is measured in meters per second per second. Or meters per squared.

Calculating Acceleration A jet starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is its acceleration? What is the final velocity? What is the initial? What is the total time?

Calculating Acceleration A jet starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is its acceleration? Acceleration (a) = final velocity (vf) – initial velocity (vi) time (sec) a = 80 m/s – 0 m/s 20 sec a=4m/s/s What is the final velocity? What is the initial? What is the total time?

Calculating Acceleration A skateboarder is moving in a straight line at a speed of 3 m/s and comes to a stop in 2 sec. What is his acceleration? a = 0 m/s - 3 m/s 2 s a=-1.5 m/s/s Acceleration (a) = final velocity (vf) – initial velocity (vi) time (sec) What is the final velocity? What is the initial? What is the total time?

Calculating Acceleration Acceleration (a) = final velocity (vf) – initial velocity (vi) time (sec) a = 16 m/s - 0 m/s 4s a= 4 m/s/s Look at the images of the cars. What is the final velocity of the car? What is the initial? What is the total time? 0 s 1 s 2 s 3 s 4 s 0 m/s 4 m/s 8 m/s 12 m/s 16 m/s

Calculating Acceleration A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver’s average acceleration? Acceleration (a) = final velocity (vf) – initial velocity (vi) time (sec) a = 40 m/s - 20 m/s 2s a= 10 m/s/s What is the final velocity? What is the initial? What is the total time?

Calculating Acceleration An airplane accelerates off the ground from 50 m/s and reaches cruising at 100 m/s. What is the airplane’s average acceleration? Acceleration (a) = final velocity (vf) – initial velocity (vi) time (sec) Average acceleration can’t be determined! You don’t know the time in which is changed velocity

Think Aloud Is it acceleration if a bird changes direction while in flight? What type of acceleration does the second hand on a clock demonstrate? If a car gains speed as it backs up, is this negative acceleration? 1. No. It is positive acceleration because it is speeding up. 2. Yes. A change in direction is acceleration. 3. A second hand is an example of centripetal acceleration

OUT Alex is observing a car race. As the car turnsa corner, it is traveling at 80km/hr. As the car crosses the finish line, it is traveling at 140km/hr. Which term describes these measures? Speed Velocity Average speed Average velocity