 Acceleration is a change in velocity by  Changing speed: ▪ Starting ▪ Stopping ▪ Speeding up ▪ Slowing down  Or changing direction

 Acceleration can be positive or negative  Speeding Up – Positive acceleration (+)  Slowing Down – Negative acceleration (-)  Units – measured in m/s 2  Acceleration is caused by unbalanced forces  Calculating Acceleration: Final Speed – Initial Speed Time

 A way to describe motion.  Average speed - Rate of motion calculated by dividing the distance traveled by the amount of time it takes to travel that distance  Constant speed - Speed that does not change  Instantaneous speed - Speed of an object at any given time  Units: Measured in m/s

Speed is calculated by dividing distance by time. Distance Time Speed =

Divide Distance by Time Distance ÷ Time = Speed Speed = Distance ÷ Time

Multiply Speed and Time Distance = Speed X Time Speed X Time = Distance

Divide Distance by Time Distance ÷ Speed = Time Time = Distance ÷ Speed

 A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?

A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running? Speed = Distance ÷ Time Speed = 100 m ÷ 20 s Speed = 5 m/s Remember to include the UNITS!!

 Velocity is speed with direction  Calculating velocity is the same as calculating speed (distance/time).  The difference is that velocity is what physicists call a vector.  There must be direction.  Speed = 3 m/s  Velocity = 3 m/s, heading northeast Velocity = Final Distance – Initial Distance Final Time – Initial Time Velocity = Final Distance – Initial Distance Final Time – Initial Time

 Speed describes distance and time  Velocity describes distance, time, and direction  You can say the top speed of an airplane is 300 kilometers per hour (kph). But its velocity is 300 kph in a northeast direction.

Which of the following sentences contain an example of velocity and which contain an example of speed? A. Five seconds into the launch, the rocket was shooting upward at 5000 meters per second. B. Cheetahs can run at 70 miles per hour. C. Moving at five kilometers per hour, it will take us eight hours to get to the base camp. D. The car covered 500 kilometers in the first 10 hours of its northward journey. E. Roger Bannister was the first person to run one mile in less than four minutes. Velocity Speed

 Podcast Podcast

Velocity Time Distance m/s m/s 2 Speed Acceleration Direction Time m/s m/s north m/s 2 Distance Direction m/s north