Speed Project

8th grade is working on a speed project that will be due next Friday, September 20th. They will be calculating the speed that common objects travel. They will need to pick three objects and measure the distance the object travels and the time it takes to find the speed. ALL MEASUREMENTS MUST BE DONE IN THE METRIC SYSTEM-no credit for any work involving standards units (in, ft, etc).

Students can do this for any three objects, but it must be repeatable because they have to have 3 trials for each. They must have three different objects to measure, that means they may NOT measure how fast mom, dad, and sister walk 50m. I would only count one of those. Ideas: speed of a ball thrown, riding a bike, dog running, ant crawling, air freshener travels across a room, candle melting, soap dripping, whatever!

Students will create a display card that gives a title, a diagram, a data table, and the procedures. They will create one card for each set of measurements. The title should be something creative that tells us exactly what the measurements were. The diagram can be a picture taken or a hand-drawn diagram to show what was done. The procedures need to be detailed and something that another person could follow without any prior knowledge of the experiment. The data table should have space for the trials, distance (probably the same for each trial), the time, and speed. They will also need to calculate the average, so this can be included in the data table. Here is an example of a generic data table. All number must always have units. A number without units is just nonsense and not helpful.

Trials	Distance	Time	Speed
1
2
3
Average

Calculating Speed

Speed = Distance / Time

This is fairly straight forward. If you are given a distance (km, m, or some ridiculous unit such as miles) and a time (hr, min, sec); you simply divide the distance by the time. The unit for speed would be km/hr, m/s, or something similar (we here mph very often which is miles/hr).

Trying to determine how far an object will travel and how long a trip will take can be simple as well. You could do a little algebra and rearrange your variables or you can remember our simple triangle.











We glued one into our notebooks! The triangle will give you the equation you need if you simply cover up the measurement you are looking for. Looking for the distance? Cover up the D and you get Speed x Time, so D = S x T. Time? Cover up the T for Distance / Speed or T = D / S!

Example:

1. Ms. Walls is running away from zombies at 3 m/s. If safety is 60 m away, how long will it take Ms. Walls to reach safety? Since we are looking for a time, our equation is  T=D/S, now we fill in the information we are given.
• T = 60 m / 3 m/s (since we have m on top and m on bottom, our unit cancel and we have s)
• T = 20 s
• Does this make sense? Double check your number and units! 

Always pay attention to the units you are given and the units you are asked to give your answer in.

1. Snoopy has flown his doghouse 15 km and it has taken him 30 min. What is his speed in km/hr? The easiest way to solve this is to convert 30 min to hr. Since there are 60 min/hr; divide 30 min by 60 min/hr to get 0.5 hr. Then, find the speed. S=D/T, so S= 15 km / 0.5 hr = 30 km/hr.

 

Speed and Velocity (8th)

Speed is a rate, or a number that tells us how fast something happens. In this case, it tells us how fast a distance is traveled. For example, if someone rides a bike 2 m/s, they are traveling 2 meters every second. We could use that to track how far they have traveled for a certain amount of time or how long it would take them to arrive at a destination. We often here speed measured in mph or miles per hour; which would tell us how far someone would get if they traveled for an hour at a constant speed.

There are two types of speed. We could look at average speed, the total distance traveled / total time it takes. Average speed would be what you calculate for a race or road trip: John traveled 12 km to the store and it took 20 min to get there. We simply look at how far he traveled and how long it took. Stoplights, changes in speed, etc don't matter here. Instantaneous speed is a measure of how fast on object is traveling at a given instant in time. For example, if you get pulled over for speeding, the cop tells you how fast you were traveling when he caught you with his radar.

Velocity is similar to speed, but it has a direction. Two ways to change velocity are to change speed or change direction. Objects very rarely have a constant velocity for long because objects usually change speed or direction frequently.