How do you think scientists can visualize acceleration?• A motion graph

What are the two kinds of graphs we have discussed?• Position vs. Time• Speed vs. Time

Jennifer Brown

GRAPHING MOTION

The position vs. time position vs. time graph is a curve when there is acceleration.

The car covers more distance each second, so the position vs. time graph gets steeper each second.

Jennifer Brown

Sections 4.1-4.3

When a car is slowing down, the speed decreases so the car covers less distance each second.

The position vs. time graph gets shallower with time.

Jennifer Brown

Sections 4.1-4.3

Jennifer Brown

Sections 4.1-4.3

An object is in free fallfree fall if it is accelerating due to the force of gravity and no other forces are acting on it.

http://fragg.me/video/solving-rubiks-cube-skydiving

Jennifer Brown

Sections 4.1-4.3

SECTION 4.2 – GRAPHING MOTIONSECTION 4.2 – GRAPHING MOTION : :

Constant speed –• the speed stays the same

An object moving at constant speed always creates a position vs. time graph that is a straight line.

Sections 4.1-4.3October 19-20, 2011

Graphs of Motion:

• The data shows the runner took 10 seconds to run each 50-meter segment.

• Because the time was the same for each segment, you know the speed was the same for each segment.

Sections 4.1-4.3October 19-20, 2011

Sections 4.1-4.3October 19-20, 2011

You can use position versus time graphs to compare the motion of different objects.

The steeper the line on a position vs. time graph means a• faster speed.

Is this a direct or indirect relationship?• Direct relationship

Sections 4.1-4.3October 19-20, 2011

The steepness of a line is measured by finding its slope.

The slope of a line is the ratio of the “rise” (y axis) to the “run” (x axis).

Sections 4.1-4.3October 19-20, 2011

Sections 4.1-4.3October 19-20, 2011

Calculating Distance (Speed Vs. Time Graphs):• Suppose we draw a rectangle on the speed vs. time

graph between the x-axis and the line showing the speed.

• The area of the rectangle is equal to its length times its height.

Sections 4.1-4.3October 19-20, 2011

Graphical Relationships:

Sections 4.1-4.3October 19-20, 2011

No relationship between variables

Sections 4.1-4.3October 19-20, 2011

Weak relationship between variables

Sections 4.1-4.3October 19-20, 2011

Direct Relationship between variables

Acceleration is easy to spot on a speed vs. time graph.

Acceleration causes the line to slope up on a speed vs. time graph.

What is the bike’s acceleration?

Jennifer Brown

Sections 4.1-4.3

If the hill is steeper, what do you think happens to the acceleration?

• The acceleration is greater.

Jennifer Brown

Sections 4.1-4.3