Content

• Steps
• Method 1 of 3: How to Measure a Runner's Speed
• Method 2 of 3: How to measure the speed of sound
• Method 3 of 3: How to Measure Wind Speed
• Tips
• What do you need

Speed ​​indicates how fast the object is moving. The speed of an object is the distance traveled in a certain time. Usually, speed is measured in meters per second (m / s), kilometers per hour (km / h), or centimeters per second (cm / s). To measure speed, you must determine the distance traveled by the object and the time it took, and then divide the distance by the time.

Steps

Method 1 of 3: How to Measure a Runner's Speed

1. 1 Find the distance the runner needs to cover. This distance can be determined from a known track length (eg 100 meters) or direct measurements.
   • Use a tape measure or staff to determine the unknown distance.
   • Mark the start and finish with ribbons or signal cones.
2. 2 Prepare for an experiment. To determine the speed of a runner, it is necessary to measure the time it takes for him to cover the target distance. Ask the runner to wait until you say, "March!" - this will allow you to accurately record the time using a stopwatch. Set the stopwatch to zero and ask the runner to take the starting position.
   • Time can also be measured with a conventional watch, although the measurement result will be less accurate.
3. 3 Give the runner the start signal and start the stopwatch at the same time. Try to synchronize these actions as accurately as possible. Shout "March!" - and immediately turn on the stopwatch. If you can't do this at the same time, give the runner a hang-up signal and try again.
4. 4 Stop the stopwatch as soon as the runner crosses the finish line. Watch the runner carefully so as not to miss the moment when he crosses the finish line. Try to record this moment as accurately as possible and immediately stop the stopwatch.
5. 5 Divide the distance traveled by the runner by the number of seconds spent. The result is the runner's speed. The formula for determining the speed is as follows: distance covered / time taken. Suppose a runner ran 100 meters in 10 seconds. Then its speed is 10 m / s (100 divided by 10).
   • To express the runner's speed in kilometers per hour, multiply 10 m / s by 3600 (the number of seconds in one hour). The result is 36,000 meters per hour, or 36 kilometers per hour (1 kilometer equals 1,000 meters).

Method 2 of 3: How to measure the speed of sound

1. 1 Find a wall that reflects sound well. A large brick or concrete wall works well for this experiment. To test how the wall reflects sound, clap your hands or shout loudly and listen for the echo. If you hear a distinct echo, the wall is good for your purpose.
2. 2 Measure at least 50 meters from the wall. This distance is necessary in order for you to have enough time for sufficiently accurate measurements. Since the sound first travels the distance from you to the wall and then returns back to you, the distance is actually 100 meters.
   • Determine the distance with a measuring tape. Try to make it as accurate as possible.
3. 3 Clap your palms together with the sound of the echo from the wall. Stand at the measured distance from the wall and begin to slowly clap your palms. When you do this, you will hear an echo. Speed ​​up or slow down and adjust the rhythm so that each next clap matches the echo of the previous clap.
   • When you achieve complete synchronicity, you will hear only your claps and you will no longer hear the sound of the echo.
4. 4 Clap your palms 11 times and record this time with a stopwatch. Ask your friend to start the stopwatch at the first clap and stop at the same time as the last. If you slap 11 times, then the sound will have time to reach the wall 10 times, bounce off it and return back in the form of an echo. Thus, the sound will travel a distance of 100 meters 10 times.
   • Plus, 11 claps will give your friend enough time to accurately start and stop the stopwatch.
   • To get more accurate results, do this several times and find the average. To find the average, add all the time intervals obtained and divide by the number of measurements.
5. 5 Multiply the distance by 10. Since you clapped your hands 11 times, the sound traveled 10 times. Multiply 100 meters by 10 to get 1000 meters.
6. 6 Divide the distance traveled by the sound by the time it took you to clap 11 hands. As a result, you will get the speed of sound with which it covered the distance from your palms to the wall, and then back to your ears.
   • Let's say 11 claps took 2.89 seconds. To find the speed of sound, you need to take the distance, that is, 1000 meters, and divide it by this time. As a result, you get 346 m / s.
   • The speed of sound at sea level is 340.29 m / s. Your result should be close to this value, but not necessarily exactly the same, especially if you are not at sea level. The higher the altitude, the thinner the air, and the slower the sound propagates.
   • Sound travels faster through liquids and solids than through air. The higher the density of the medium, the higher the speed of sound.

Method 3 of 3: How to Measure Wind Speed

1. 1 Take out the anemometer. An anemometer is a device for measuring wind speed. It consists of 3 or 4 cups, which are mounted on knitting needles that rotate around a central axis. The wind blows into the cups and turns the spokes. The higher the wind speed, the faster the cups rotate around the axis.
   • You can buy an anemometer or make it yourself.
   • To make your own anemometer, take five 100 ml paper cups, two straws, a sharpened pencil with an eraser on the back, a stapler, a small sharp safety pin, and a ruler. Color the sides of one cup so you can distinguish it from the others.
   • Punch a hole in the side of one cup about 2.5 centimeters from the top. In the fifth cup, make four equally spaced holes about 2.5 centimeters below the top edge. Also, poke one hole in the bottom of this cup.
   • Take one glass and thread the straw through the side of it so that it goes in about 2.5 centimeters. Use a stapler to pin the straw to the side of the cup. Pass the remaining part of the straw through the fifth cup with four side holes so that it enters one hole and exits the opposite. Place a second cup on this end of the straw and secure it with a stapler.These cups should be facing in the same direction.
   • Repeat the above step with the other two cups and thread a straw through the remaining two holes in the middle (fifth) cup. These cups should also face in the same direction.
   • Carefully thread the pin through the straws where they intersect in the middle cup.
   • Slide your pencil through the hole in the bottom of the fifth cup and insert a pin into the eraser. Make sure the anemometer rotates freely. If the straws with the cups on them are spinning freely, the anemometer is ready for use. If not, adjust the position of the pencil so that the eraser does not hit the straws.
2. 2 Calculate circumference anemometer. This length is equal to the distance that one of the cups travels at a full turn of the anemometer. To calculate the circumference of a circle, you need to measure its diameter.
   • Measure the distance from the central axis of the anemometer to the center of one of the cups. This is the radius of the anemometer. Multiply the radius by two and you get the desired diameter.
   • The circumference of a circle is equal to its diameter (or twice its radius) times pi.
   • For example, if the distance between the center of the cup and the center axis of the anemometer is 30 centimeters, the cup travels 2 x 30 x 3.14 in one full revolution (here pi is rounded to two decimal places), or 188.4 centimeters.
3. 3 Position the anemometer where the wind is blowing. The wind should be strong enough to rotate the axis of the anemometer, but not deflate or overturn it. It may be worthwhile to attach the anemometer to the ground or a rigid rod so that the pencil is vertical.
4. 4 Count the number of revolutions of the anemometer over a certain period of time. Stand next to the anemometer and count how many revolutions the painted cup will make. The time interval can be 5, 10, 15, 20, 30 seconds or even a whole minute. For more accuracy, use a timer.
   • If you don't have a timer, ask a friend to time the time while you are counting the number of revolutions.
   • If you are using a commercially available anemometer, mark one cup somehow to get the correct rpm count.
5. 5 Multiply the number of revolutions by the distance the cup travels in one revolution, that is, by the circumference of the anemometer. Thus, you will find the distance that the glass travels in the time interval you selected.
   • For example, if the radius of the anemometer is 30 centimeters, the cup travels a distance of 188.4 centimeters in one revolution. If you have counted 50 revolutions in the selected time interval, then the total distance is 50 x 188.4 = 9420 centimeters.
6. 6 Divide the total distance by the elapsed time. Speed ​​is defined as the distance divided by the time it takes to travel that distance. Thus, if you divide the found total distance by the selected time interval, then determine the current wind speed.
   • For example, if you counted the number of revolutions in 10 seconds, you should divide the total distance by 10 seconds. Velocity = (9420 cm / 10 s) = 942 cm / s.
   • If you multiply 942 cm / s by 3600, you get 3391200 cm / h, and if you divide by 100,000 (the number of centimeters in one kilometer), you get 33.9 km / h.

Tips

• In physics, speed is a vector quantity, that is, it is set not only by a numerical value, but also by the direction in which the object is moving. The anemometer rotates in a circle, so it only shows the wind speed and does not provide information about its direction. The direction and approximate speed of the wind can be judged by the windsock, which is inflated with air and rises in the direction in which the wind is blowing.

What do you need

• Stopwatch
• Assistant
• Treadmill (to measure the speed of a runner)
• Sound-reflecting wall (for measuring the speed of sound)
• Roulette (for measuring the speed of sound)
• Anemometer (for measuring wind speed)