Site hosted by Angelfire.com: Build your free website today!

Describing Motion

Chapter 2


  1. Speed
    1. Average Speed
    1. Instantaneous Speed
  1. Velocity
    1. Instantaneous Velocity
    1. Average Velocity

C) Application: Racing Car Tires

  1. Acceleration
    1. Instantaneous acceleration

 

    1. Average acceleration

a = v/t = (vf vi)/t



t = 5 s


v1 = 0 m/s v2 = 20 m/s

a = v/t = (vf vi)/t

a = (20 m/s 0 m/s)/5 s

a = 4 m/s2

    1. Direction of an acceleration




v1 v2



a





v1 v2



a


The velocity of a car decreases from 30 m/s to

15 m/s in a time of 3 seconds. What is the average acceleration of the car?




v1 = 30 m/s v2 = 15 m/s


a = vf vi/t = (15 m/s 30 m/s)/3s = -5m/s2


a m/s2

 

 

  1. Graphing Motion
    • Graph => Provides an overview of what happened.

Time

Distance

0 sec

0 cm

5 sec

4.1 cm

10 sec

7.9 cm

15 sec

12.1 cm

20 sec

16.0 cm

25 sec

16.0 cm

30 sec

18.0 cm

35 sec

21.0 cm

 

 

 

 

 

 

 


 

 

 


 

 

 

 

  1. Uniform Acceleration
    1. How does velocity vary with uniform acceleration?
    2. v = vo + at

    3. How does distance vary with time?

* If the object starts from rest:

d = 1/2 at2

* If the object is moving before it begins to accelerate:

d = vot + at2