 Acceleration: When an object changes velocity, it undergoes acceleration.  Acceleration (a) = (v f - v i )/t Change in speed = v f - v i v i = (initial or starting speed) v f = (final or ending speed)  Acceleration is the slope of the speed vs. time graph.

Unit of acceleration: Unit of speed/unit of time = m/s =m/s 2 s  Negative acceleration: Decreased speed in given amount of time. It is written with negative sign.  Negative acceleration is also defined as Deceleration.  Positive acceleration: When the speed of an object is increasing in the same direction as the motion.

Centripetal acceleration: Uniform circular motion has Centripetal acceleration. For example, windmills are constantly changing direction as they travel in a circle, so centripetal acceleration is occurring. Find out positive. Negative and Zero acceleration In this graph.

Calculation of acceleration Natalie accelerate her skate board along a straight path from 0 m/s to 31 m/s in 20 s. Find her average acceleration.

Home work: 1)Page-377 Section-11.2, answer 1 to 6 2)Do practice problem Page # to 5 Page # & 2 3)Page-391Answer 17, 18 4)Page 391 do # 26