Velocity is a measure of how fast an object is moving. The object's speed is the total distance traveled in a given time. The units for speed are miles per hour (miles/hour or mph), centimeters per second (cm/second or cm/s), meters per second (m/second or m/s), or kilometers per hour (km/hour or kph). To measure speed, you need to know the distance an object has traveled and the time it has traveled, then calculate the speed by dividing the distance by the time.
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Method 1 of 3: Measuring Runner Speed
Step 1. Determine the distance to be covered
You can tell if the runner is on a track of known length, such as 100 m, or by observing the distance in an open field.
- Use a tape measure to measure distance if you are in the field.
- Mark the start and end points with a rope or road marking cone.
Step 2. Start the experiment
To find the runner's speed, you need to know the time it will take him to cover the specified distance. Ask him to wait until you say “Start!” so that the measurement on the stopwatch is accurate. Make sure the stopwatch shows zero, then ask the runner to get ready at the starting position of the distance to be measured.
You can also use a watch to measure time, but the results are not very accurate
Step 3. Signal the runner while watching the stopwatch
Try to match the timing, shout “Start!”, and check the stopwatch at the same time. If you notice the stopwatch is off, have it restart.
Step 4. Stop the stopwatch when the runner crosses the finish line
Pay close attention to whether the runner has passed the designated point as the finish line. Make sure the stopwatch is turned off just as it crosses the line.
Step 5. Divide the distance the runner traveled by the time it took
This division is a calculation of the runner's speed. The velocity equation is the distance traveled/time traveled. With the example of a distance of 100 m (328 ft), if the runner takes 10 seconds to cover the distance, his speed is 100 m (328 ft) divided by 10, or 10 m/s (32.8 ft per second).
- By multiplying 10 m/s by 3,600 (the number of seconds in an hour), the runner covers 36,000 meters per hour, or 36 km/h (10 kilometers equals 1,000 m).
- By multiplying 32.8 feet per second by 3,600, the runner covers 118,080 feet per hour, or 22.4 miles per hour (1 mile equals 5,280 feet).
Method 2 of 3: Measuring the Speed of Sound
Step 1. Find a wall that reflects sound
You can use stone or concrete walls for this experiment. Test the wall by clapping or shouting, and listen for the echo. If you hear a loud echo, the wall is good to work with.
Step 2. Measure a distance of at least 50 m from the wall
A distance of 50 m is recommended as it gives you enough time to take accurate measurements. Since you are considering the distance the sound will travel from you to the wall and back to you, you are actually measuring a distance of 100 m).
Measure the distance with a tape measure. Try to measure as accurately as possible
Step 3. Clap your hands when the echo comes from the wall
Stand in front of the wall at the measured distance, and clap your hands lightly. At that point, you should be able to hear the echo. Increase or decrease the speed of the clapping rhythm until it coincides with the echo of the previous clapping.
When the sync is perfect, you shouldn't be able to hear the echo, only the clapping
Step 4. Clap your hands 11 times while recording the time with the stopwatch
Have a friend turn on the stopwatch on the first clap and stop on the last. By clapping your hands 11 times, you measure 10 intervals of the distance the sound of clapping echoes from the wall. In essence, sound travels 10 times the distance of 100 meters.
- Clap 11 times also gives your friends time to start and stop the stopwatch accurately.
- Do this step a few times and find the average time to get a more accurate measurement. To find the average, add up all the times obtained and divide by the number of trials.
Step 5. Multiply the distance by 10
Because you tap 11 times, the sound travels 10 times the distance. 100 meters multiplied by 10 is 1000 meters.
Step 6. Divide the distance the sound travels by the amount of time it takes to clap
This counter measures the speed of sound clapping from your hand to the wall and back to your ear.
- For example, you need 2.89 seconds to clap 11 times. Divide the distance of 1,000 meters by 2.89 seconds to get the speed of sound of 346 m/s.
- The speed of sound at sea level is 340.29 m/s (1,116 feet per second or 761.2 miles/hour). Your calculations should be close to that number, but they may not be the exact same, especially if you're not at sea level. At higher altitudes, the air is thinner and the speed of sound is slower.
- The speed of sound is higher when it travels through liquids and solids than through air because sound travels faster when it passes through high density materials.
Method 3 of 3: Measuring Wind Speed
Step 1. Prepare the anemometer
Anemometer is a device that measures wind speed. This tool consists of 3 or 4 bowls with bars each mounted on a rotating shaft. The wind will enter the bowl and make the bowl spin. The faster the wind blows, the faster the bowl rotates on its axis.
- Anemometers can be purchased or made yourself.
- To make an anemometer, prepare five paper bowls, two straws, a sharp pencil with an eraser, a stapler, a sharp pin, and a ruler. Color one bowl to distinguish it from the others.
- Punch a hole in one side of the four bowls, about 2 inches from the edge. In the fifth bowl, make four evenly spaced holes around the bowl, about 2 inches from the edges. Also, make a hole in the bottom of the bowl.
- Insert a straw through the side of one of the bowls, making sure there is a 2-inch end of the straw in the bowl. Clamp the ends to the sides of the bowl with a stapler. Insert the other end of the straw through the fifth bowl with 4 holes on one side and out on the other. Place a second bowl at the end of this straw and secure it with a stapler. Make sure all the bowls are facing the same direction.
- Repeat the above steps with the other two bowls, inserting the straws into the two remaining holes in the center bowl. Again, make sure all the bowls are facing the same direction.
- Carefully insert the pin at the intersection point of the straws in the center bowl.
- Insert the pencil into the bottom hole of the fifth bowl and guide it through the pin until it hits the eraser. Make sure the anemometer can rotate smoothly. If not, adjust the position of the pencil so that the eraser is not pointing directly at the straw.
Step 2. Calculate the circumference of the anemometer
When one of the bowls completes one full rotation, the distance it travels is the circumference of the circle. To calculate the circumference, you must measure the diameter of the circle.
- Measure the distance from the center of the anemometer to the center of one of the bowls. This is the anemometer radius. The diameter is 2 times the radius.
- The circumference of a circle is equal to the diameter times the constant pi, or 1 times the radius times pi.
- For example, if the distance between the center of the bowl and the center of the anemometer is 30 cm (1 ft), the distance the bowl travels in one rotation is 2 x 30 x 3.14 (rounded pi to 2 decimal places), or 188.4 cm (74.2 cm). inch).
Step 3. Place the anemometer where the wind hits the bowl
You need enough wind to turn the anemometer, but not so much that it blows it loose. If necessary, add weight to allow the anemometer to stand upright.
Step 4. Count the number of times the anemometer rotates to find out the fixed time duration
Stand motionless at one point and count the number of times the colored bowl revolves around the circle. The possible intervals are 5, 10, 15, 20, 30 seconds, or even 1 full minute. Set the stopwatch to turn off at specific time intervals to ensure counting accuracy.
- If you don't have a stopwatch, have a friend look at the clock when you're counting rotations.
- If you purchased a ready-made anemometer, mark one of the bowls so that it can count correctly.
Step 5. Multiply the number of rotations by the distance the anemometer travels in one revolution
The result is the total distance the anemometer traveled at the time of your observation.
For example, an anemometer has a radius of 30 cm (0.98 ft). Thus, the anemometer travels 188.4 cm (6.18 ft) in one revolution. If it rotates 50 times as long as you count, the total distance is 50 x 188, 4 = 9,420 cm
Step 6. Divide the total distance by the travel time
The formula for speed is the total distance divided by the amount of time it takes to cover that distance. To calculate the wind speed at the time of observation, take the total distance traveled by the anemometer and divide by the travel time.
- For example, if you're counting the number of rotations in 10 seconds, divide the distance covered by 10 seconds. Speed = 9,420 cm/10 sec = 942 cm/sec (30.9 ft/sec).
- Multiplying 942 cm/s by 3,600 gives 3,391,200 cm/h, divided by 100,000 (the number of centimeters in a kilometer) to 33.9 km/h.
- Multiplying 30.9 feet per second by 3,600 yields 111,240 feet per hour, divided by 5,280 gives 21.1 miles per hour.
