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Motion Graphs

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(d vs t)

 

 

RollingDown

B. Interpreting Motion Diagrams

 

Acceleration Review

Acceleration - the time rate of change in velocity  

 

a = ∆V/∆t = (Vf - Vi)/t

 

 

 

Uniform Acceleration?

 

 

 

- constant  change
in velocity per unit time

 

 

Which data shows uniform acceleration? Why?



time
(sec)
Velocity
(m/s)
0 5
1 7
2 9
3 11
4 13
time
(sec)
Velocity
(m/s)
0 5
1 10
2 14
3 20
4 30

 

 

 

Left Data Shows Constant Acceleration

a = ?

 

 

a = 2 m/s2

 

 

 

Non-Constant Acceleration or NOT?

 

Ex) Describe the acceleration

 

acceleration is constant +

 

Non-Constant Acceleration or NOT?

 

Prove this is constant acceleration

  

 

Every 2 seconds
the object gains
exactly 15 m/s


 

 

 

 

 

Motion Map

Velocity

0 m/s / 15 m/s / 30 m/s / 45 m/s

0 sec / 2 sec / 2 sec / 2 sec

 

 

 

 

Find the acceleration 

 

 

a = ∆V/∆t

 

(+15 m/s)/2 sec 

 

 

a = +7.5 m/s2

 

 

 

 

 

 

Motion Map

 

Acceleration

 

 

 

 

 

2 sec / 2 sec / 2 sec / 2 sec

+7.5 m/s2/+7.5 m/s2/+7.5 m/s2/+7.5 m/s2

 

 

Motion Map

Displacement

 

 

 

Slope of a V vs. t plot

Slope = ∆y/∆x

= ∆V/∆t = a

 

Ex)

Describe motion using
y axis and slope

Step 1: y axis:

Step 2: Slope

 

Answers

Step 1: y axis: V constant

 

 

Step 2: Slope = ∆V/∆t  = a

a = 0

 

 

Ranking Task

Rank the acceleration from largest to smallest

 

January 2001 Regents

 

 

 

 

 

Ex 4)

Step 1: y axis:

 

 

Step 2: Slope

 

Answers

 

Velocity is Decreasing,

 

Acceleration is
constant
, negative

 

 

Calculate the acceleration

 

 

a = (Vf- Vi)/t

 

 

 (15 m/s - 45 m/s )
    (8 sec - 2 sec)

 

 

 

= -5 m/s2

 

 

Ex 5) Describe the motions

Velocity (m/s)

   

Step 1: y axis:

Step 2: Slope

 






Answers

Step 1: y axis:  V increasing

 

 

Step 2: Slope = ∆V/∆t  = a

a is increasing

 

Ex) Describe the motions

 

Step 1: y axis:

Step 2: Slope

 

 

 

 

 

Step 1: y axis: d increasing

Step 2: Slope = d/t = V

 

Velocity is increasing smoothly

 Acceleration is constant & Positive

 

Non-Uniform Acceleration

 

Ex)

Describe motions

Step 1: y axis:

Step 2: Slope

 

 

 

 

 

Step 1: y axis: d increasing

Step 2: Slope = d/t = v

Velocity is Decreasing smoothly

(slope)

 

Acceleration is

constant & negative

 

 

 

 

Describe motions

d (cm)

Step 1: y axis:

Step 2: Slope

 

 

 

Step 1: y axis: d constant

Step 2: Slope = d/t = v

 

v = 0 (slope)

a = 0

 

 

 

 

Analyzing Motion Plots - HTML5
St. Mary's H.S.

[Flash]

 

Summary

 

 

 

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