Graphing Motion in One Direction Section 5.1 Physics

Objectives Interpret graphs of position versus time for a moving object to determine the velocity of the object. Describe in words the information presented in graphs and draw graphs from descriptions of motion. Write equations that describe the position of an object moving at constant velocity.

Position Time Graphs Position-time graphs can be used to find out the location of an object at time instant. What is a time instant? An instant is shorter than any measurable amount.

Where is the car at 6 seconds?

More Than One Object Graphs can display the motion of more than one moving object. Where the lines (on a line graph) intersect is where the objects meet.

Two or More Objects

Example Problems Describe the motion of the 4 walkers. Walks east at a constant velocity. East Walks east at a constant velocity that is slower than Walker B. B High St. Walks west of High St. First quickly, then slows to a stop. C West D Starts east of High St. and walks west at a constant velocity.

Example Problems Describe the motion of the car.

Example Problems When was the car 20m west of the origin? East West

Example Problems Where was the car at 50 s?

Example Problems The car suddenly reversed directions. Where and when?

Different Types of Motion Uniform Motion: Equal displacements occur during successive equal time intervals.

Using Uniform Motion Graphs A uniform motion graph can give valuable information, such as slope.

Slope Slope = v = Δd / Δt

Practice Problems Pg. 87 4,5,7,8

Using an Equation to Find Where and When Recall the equation for average velocity. v = Δd / Δt v = d1 – d0 / t1 – t0 If you choose your axis for time to start at 0 seconds, t0 can be eliminated since it equals zero. d1 = d0 + vt1

A Few Modifications We will be working with constant velocity, so average velocity will be treated as the constant velocity value. The equation then becomes: d = d0 + vt

Practice Problems Pg 89 9-11