Bell Ringer

25 June 2009

• LT: Interpret a distance-time graph to properly describe the motion of an object.

• Discuss with your team how the motion of an object can be described with a graph.

Describe tumble buggy motion

• Define the system - What must we include; what may we disregard?

• Define the variables - What aspects are likely to change in our description of the motion?

Making a distance-time graph

• Start your stopwatch when car passes the starting line.

• Every 5 seconds place a washer beside the tumble buggy’s position (distance measured from the starting line).

• Record distance and time, and make a d-t graph.

Interpreting a dist-time graph

Best-fit Line for Tumble Buggy

• Determine expected model of best-fit line (e.g., proportional, linear, inverse).

• Determine if line must pass through origin.• Fit line so that it minimizes the sum of all vertical

deviations (residuals) from that line.

Correct Fit Minimize Residuals

Interpreting Slopes

• To find slope, identify two points on best-fit line.

• Identify one point’s coordinates as (xP, yP) and the other point’s coordi-nates as (xR, yR).

• Calculate slope = change in y divided by change in x.

• Slopes can be + (a and b), - (c and d), 0 (horizontal), or infinite (vertical).