6th grade Physical Science Lesson
Topic: Physics of Motion
Activities: Balloon Racer, “How fast is a Cheetah?” a unique comparison of animals fast and slow by Rand McNally
Remember, some of the greatest scientific discoveries have been made by mistake!
From the TEKS:
TLW: -apply what they know about force and motion to design the fastest balloon racers.
-identify and describe the changes in position, direction, motion, and speed of an object when acted upon by an unbalanced force.
-calculate average speed using distance and time measurements
*investigate how inclined planes can be used to change the amount of force to move an object (not expected of all students)
Background Information:
A lesson on mechanics must include a discussion of Sir Issac Newton’s Philosophiae Naturalis Principia Mathematica, which includes the three axioms, or laws of motion (published in July 1687). His first law states that any object at rest will remain at rest and any object in motion will remain in constant (no change in direction) and uniform (no change in velocity) motion (no change in acceleration) unless acted upon by an outside force (inertia). (Don’t forget: there are other forces like friction and gravity that must be considered in a study of motion/inertia). Velocity is dependent on the force and time applied. In order to understand Newton’s first law, we must look at his second law: force equals mass times acceleration. F=ma. Acceleration is the change in direction or velocity of an object. A moving object can speed up, sow down, or be turned which all require a push or pull which is delivered as a force. From this formula, we can compare various amounts of mass to acceleration for a given force. Newton’s third law states that for every action there is an equal and opposite reaction. In our balloon racer activity, we will consider the action as the backward force of escaping air and the reaction (equal and opposite) as the forward acceleration of the balloon.
Vocabulary:
Reference point: a place or object used for comparison to determine if something is in motion
Motion: an object is said to be in motion when the distance from the object to another object (reference point) is changing
Speed: rate of motion, distance/time (we will measure speed in m/s)
Velocity: rate of change of position, (speed in a given direction)
Acceleration: rate in change of velocity; increase/decrease in speed, or changing direction
Force: a push or pull which can cause an object to start/stop moving or change the way that an object is moving
Newton’s Laws of Motion:
(1) Every body continues in its state of rest, or uniform motion in a straight line, unless it is compelled to change that state by forces impressed on it (inertia).
(2) The change in motion is proportional to the motive force impressed and is made in the direction of the straight line in which that force is impressed (F = ma).
(3) To every action there is always an opposed and equal reaction.
Date: ____________________________________________
Names of Group Members: _______________________________________________________________
Purpose: Determine how to make the fastest balloon racer.
Materials: Tape, String, Straw, Balloon, Pushpins, Stopwatch, Measuring Tape/Meter sticks, Marker/Chalk
Introduction: Moving objects have speed (rate of motion/change of distance). We determine speed by calculating how far an object travels in a certain amount of time.
Example: We measure the speed of our cars by dividing the distance traveled by the amount of time (miles/hour or mph).
The SI (International System) unit of speed is m/s (meters per second).
Procedure:
1. Pick a location outside of the classroom where your group can perform 8 trials with different track lengths.
2. Thread a straw onto a piece of yarn and attach the end of the yarn on the wall using a pushpin.
3. Run the string at least 10 meters and secure the other end to the wall.
4. Blow up a balloon, but DO NOT TIE IT. Hold the end closed.
5. Have a partner attach the straw to the balloon lengthwise with the tape (refer to Figure 1).
6. Mark the string to show the front end of the balloon.
7. Pick one member of your group to say, “Ready, Set, Go” and one member to start the stopwatch as the balloon is let go. Stop the timer when the balloon stops.
8. Mark the string where the front of the balloon stopped and measure the distance between the marks. Record this distance (in meters) on your Data Page.
9. Record the amount of time (in seconds) on your Data Page.
10. Repeat this experiment 8 times. (You can use more or less string for each trial).
Data:
| Trial Number | Distance Traveled (meters) | Time Lapse (seconds) | Speed (meters/second) |
| 1 | | | |
| 2 | | | |
| 3 | | | |
| 4 | | | |
| 5 | | | |
| 6 | | | |
| 7 | | | |
| 8 | | | |
| *Average: | | | |
*Calculate the average by adding the columns and dividing them by 8 (trials).
Average Distance Traveled:
(________+________+________+________+________+________+________+________)/8=______________
Average Time Lapse:
Average Speed (m/s):
Discussion Questions:
In which trial did the balloon travel the greatest distance? ____________________________
In which trial did the balloon travel for the longest amount of time?__________________
In which trial did the balloon have the greatest speed? ________________________________
Why do you think that trial was the fastest (had the greatest speed)?
