Acceleration is the rate at which velocity changes over time

An object is accelerating if:1. it is changing speed2. it is changing direction3. it is changing both speed and direction

Positive Acceleration – an increase in velocity (speeding up)

Negative Acceleration or Deceleration– a decrease in velocity (slowing down)

Centripetal Acceleration – The acceleration that occurs in a circular motion

Let’s Practice! Justin Timberlake is running at a velocity

of 4 ft/s South when a crazy fan starts chasing after him. Within 2 seconds he increases his speed to 8 ft/s to get away. What is his acceleration?

Average acceleration = time it takes to change velocityfinal velocity – starting velocity

A = Vf - Vi

t

A = 8 ft/s - 4 ft/s 2 s

A = 2 (ft/s)/s South or 2 ft/s2 South

1. Vf = 8 ft/s2. Vi = 4 ft/s3. t = 2 s

Average acceleration = final velocity – starting velocity time it takes to change velocity

This means that every second JT’s velocity

increases by 2 feet per second

More Practice: Calculate the bikers acceleration

Av. Acceleration = 5m/s – 1m/s = 4s

1m/s2 south

More Practice: Calculate the bikers acceleration

A plane passes over point A at a velocity of 240m/s north. Forty seconds later, it passes over point B a velocity of 260 m/s north. What is the plane’s average acceleration?

Recognizing Acceleration on a Graph

The roller-coaster moves up the hill until it stops. Then you are off! This graph shows your acceleration for the next 10 seconds. Explain:During the first 8 seconds you have (+) acceleration. Then you begin climbing the next hill so for the next 2 seconds you experience( -) acceleration

An object traveling in a circle is always changing its direction, therefore it is always changing its velocity, so it is accelerating

Examples: Windmill, Ferris Wheel, Roller Coaster Loops

1. In 0.5 seconds, a missile goes from 0 to 300 m/s. What is the acceleration?

2. A meteoroid changed velocity from 1.0 km/s to 1.8 km/s in 0.03 seconds. What is the acceleration?

3. A race car driver is moving at 200 km/min when he slams on his brakes. He comes to a complete stop in 3 mins. What is his acceleration (or deceleration)?

4. A space ship releases a satellite into orbit. The satellite falls to earth at a speed of 1700 m/s in 25 seconds. What is the acceleration?