PHY 2425 - Engineering Physics I

Motion Diagrams

Leader: _________________________ Recorder: __________________________

Skeptic: _________________________ Encourager: ________________________

Materials

Laptop

Mini DV camera with cable and battery/power adapter

Pasco Track with cart

High Contrast Meter Stick

Tripod

Introduction

This activity will introduce the subject of kinematics. Kinematics is the description of motion. We will look at several different ways to pictorially describe motion. The activity will also serve to introduce acquiring and analyzing video data which is a technique we will use frequently in this class.

Procedure

1. Set-up

Gently attach the camera to the tripod and aim it at the track so that you can see the entire track. The camera should be at the same height as the track and should be square to the track. Place the high contrast meter stick against the track in the front so that the black side faces the camera. Put the cart on the track. Double click on the LoggerPro icon to start LoggerPro.

2. Data Acquisition

Starting at one end of the track, practice giving the cart a sharp push so that it moves rapidly across the track with the wheels staying in the grooves. Once you are proficient at producing that motion, follow the procedures given in the hand out QuickStart Guide to Acquiring and Analyzing Video Data with LoggerPro to acquire a very brief video of the motion. Use the sliders to trim the film to just the portion where the cart is moving on the track.

3. Data Analysis

Follow the procedures in the handout to analyze the data. Be sure to scale the data so that the position is given in meters and not pixels.

Questions

If you turned off the trails while analyzing the data turn them back on. The trails show the location of the object at equal time intervals – 1/30^th of a second for video. A diagram showing the motion in this way is called a motion diagram.

Q1) Sketch the appearance of the trails in the space below.

Q2) Describe the spacing of the dots in the motion diagram. (i.e. increasing, constant, random,…)

Q3) What does your answer to Q2) tell you about the motion of the cart?

Examine the graph of position vs. time.

Q4) Describe in words the appearance of the graph.

Q5) What does the shape of the graph tell you about the motion of the cart?

Print and attach the graph to your report.

Q6) What feature of the graph gives the same information as the spacing of the dots in the motion diagram? Explain.

Q7) If the spacing of the dots was greater, what would this tell you about the speed of the cart?

Q8) If the spacing of the dots was smaller, what would this tell you about the speed of the cart?

Q9) If the slope of the graph was greater, what would this tell you about the speed of the cart?

Q10) If the slope of the graph was smaller, what would this tell you about the speed of the cart?

Summary Questions

S11) Sketch a motion diagram for a car moving at constant velocity.

S12) Sketch a graph of position vs. time for a car moving at constant velocity.

S13) Sketch a motion diagram for a car that is speeding up.

S14) Sketch a graph of position vs. time for a car that is speeding up.

S15) Sketch a motion diagram for a car that is speeding up.

S16) Sketch a graph of position vs. time for a car that is speeding up.