Acceleration 2.3

speed: describes the rate of change in position Define velocity. Write the formula used to calculate velocity. What is the difference between speed and velocity? speed: describes the rate of change in position velocity: describes the speed and direction of a moving object

Acceleration is the rate of change in velocity Acceleration is the rate of change in velocity. When the velocity of an object changes, the object is accelerating. Acceleration occurs when an object changes: its speed (up or down) its direction or both

Speed – Time Graphs Slop is an objects acceleration

Identify the time intervals when Tamara's car is not accelerating. 

Identify the time intervals when Tamara's car is not accelerating.  0.5–1.5 min 2–3 min 3.7–4.8 min 5.3–6 min

A speed-time graph can be used to find acceleration. Negative Acceleration Instructional approach: The teacher should present the information on the slide. Positive Acceleration

Calculating Acceleration Change in velocity is divided by the length of time Change in Velocity = final velocity – initial velocity SI Units Velocity – m/s Time – s Acceleration – m/s2 a = vf – vi t

A negative sign means in an opposite direction. Ex: - 10 m/s2 north is the same as 10 m/s2 south

Calculate Acceleration A skateboarder has an initial velocity of 3 m/s west and comes to a stop in 2 s. What is the skateboarder’s acceleration? Identify the unknown. List the knowns. Set up the problem. Solve the problem. Does your answer have a SI unit?

Circular Motion Acceleration toward the center of a curved or circular path is called centripetal acceleration.

Projectile Motion A projectile is anything thrown or shot through the air. Projectiles follow a curved path because they have both a horizontal and a vertical velocity.

Projectile Motion The horizontal velocity is constant. The vertical velocity is downward due to gravity.

If you were to throw a ball as hard as you could in a perfectly horizontal direction, would it take longer to reach the ground than if your dropped a ball from the same height? https://www.youtube.com/watch?v=oBdalzRJR5g https://www.youtube.com/watch?v=aRhkQTQxm4w Surprisingly, it will not. A thrown ball and a dropped ball will hit the ground at the same time. Both balls travel the same vertical distance in the same vertical distance in the same amount of time. However the ball thrown horizontally travels a greater distance than the ball that is dropped.

2.3 Review Define acceleration. How are acceleration, time, and velocity related? What are 3 ways an object can accelerate? How can an object’s acceleration be calculated? A cyclist starts at rest and accelerates at 0.5 m/s2 south for 20 s. What is the cyclist's final velocity? An airplane starts at rest and accelerates down the runway for 20 s. At the end of the runway, its velocity is 80 m/s north. What is its acceleration? What is centripetal acceleration? What are the similarities and differences between straight line motion, circular motion, and projectile motion?

Essential Questions How are acceleration, time, and velocity related? What are three ways an object can accelerate? How can an object’s acceleration be calculated? What are the similarities and differences between straight line motion, circular motion, and projectile motion?

New Vocabulary acceleration centripetal acceleration

Velocity and Acceleration

Assessment 1. Which of the following is the SI unit of acceleration? s/km2 A km/h B m/s2 C CORRECT cm/s D

Assessment 2. Which of the following is not used in calculating acceleration? initial velocity A average speed B CORRECT time interval C final velocity D

Assessment 3. In which of the following conditions does the car not accelerate? A car moves at 80 km/h on a flat, straight highway. A CORRECT The car slows from 80 km/h to 35 km/h. B The car turns a corner. C The car speeds up from 35 km/h to 80 km/h. D