Review of Various Videos
John L. Hubisz, Ph.D., Hubisz@unity.ncsu.edu

Playing with Physics by Paideia Productions 55 minutes VHS narrated and carried out by Eileen Romano

This is one video in a series, “Teaching Children Science” published by Paideia Productions, www.paideiaproductions.com or (800)467-1085.

The topics covered are: Speed and Distance, Velocity, Acceleration, Acceleration Due to Gravity, and Projectile Motion.

Starting with the information on the box we see, “Speed is the measure of how fast an object is moving” leaving off the very important “with respect to time.” This is important as there was the possibility, and, of course, it still could be meaningful if it were, “with respect to distance.” Making it explicit now will avoid trouble later on. Under “Velocity”, it would have been better to define scalar first, followed by vector, and then velocity. Now “velocity” can be more appropriately defined as, “is a vector quantity that is specified by a magnitude, called speed, and a direction.” There is no reason that an object rolling down an incline should be moving with constant acceleration. Projectile motion does not occur “in” an object. Other points could be made to make the remarks more acceptable.

The introductory views suggest some interesting activities for students to carry out. The presenter is enthusiastic and will appeal to young students. The constant reminder that students should do nothing without adult supervision is scary. I wonder how many of us would have become scientists and engineers being this cautious? Have you seen “October Sky”?

Speed should always be described as “distance covered divided by time taken.” “Distance divided by time” will lead to trouble later.

The example using a distance ending at the “UFO crash site” has to go. Why encourage nonsense like this? There was no UFO, and the evidence overwhelmingly supports this.

Velocity requires the specification of both magnitude and direction, not “is.”

There are rates that do not involve time, so the time units should always be explicitly mentioned. Get the students use to saying, “with respect to time.”
You cannot tell that a cart going down an incline is moving with constant acceleration.

“Gravity” is a phenomenon to be explained and there are several theories that attempt to do this. It is not a force. The force is “the force due to gravitation.” Recognizing this will keep you away from saying things like, “things fall because of gravity.”

Dropping two objects from the same height and saying that they fall with the same acceleration is fine, but one should add that even if you dropped them from different heights they fall with the same acceleration. When we assume that the gravitation force is the only force acting, we call the motion “free fall.”
Good experiment with the windup car.

The abbreviation for “second” is “s” not “sec” in SI. In addition, when describing the units for acceleration, one should write, “(m/s)/s” to emphasize velocity or speed change with respect to time. Using “m/s^2” is too complicated at this level. The abbreviation for metre is “m” not “M”.

The video has a place every once and a while to stop and review or ask questions which is a great idea.

The experiment with the parachutes is a good one, easily done and requiring students to get hands-on experience.

The path of a projectile is an arc, but it should be pointed out that it is a parabola. Although drag is appropriate, it should be mentioned that it is a form of air resistance.

A javelin thrown at 45 degrees will not yield maximum distance. This would only be the case if thrown from ground level, which, of course, it is not.

Despite my comments, this is a good attempt, but it can be significantly improved. Certainly, the ideas presented will help inexperienced teachers.