Speedclimbaverage is the measure of how quickly the position of a piece of furniture varies. The average speed can be calculated as the ratio between the total distance covered by the mobile and a given time interval.
The unit of measure of the velocity magnitude, according to the SI, is the meter per second, however, another widely used unit for this quantity is the kilometer per hour.
Lookalso: Solved exercises on uniform movement!
Average speed and average speed
Average speed is defined as the ratio of the displacement to the time interval in which a movement occurred. In this sense, the average speed is a Vector greatness, unlike the velocityclimbaverage, what is a particular case of speedaverage.
In this type of case, the movement is described without regard to its direction and meaning, therefore, it is assumed that the displacement occurs exclusively in a straight line, with no changes in the direction of movement.
The average scalar speed is, therefore, a simplification widely used in high school textbooks.
medium speed formula
The formula used to calculate average speed relates average speed to displacement and time interval, note:
vm - average speed
S – displacement
t - time interval
Read more: What is the law of speed?
Average speed formula
The average speed formula is similar to the average speed formula, however, that relates speed to total distance covered (one scalar greatness), which is different from displacement (a vector quantity). Check out:
Examples of exercises on average speed scale
Check out the step-by-step exercises on average scalar speed:
Example 1) At a less busy time, an avenue, where the maximum speed allowed is 60 km/h, is covered, in 15 minutes, by a vehicle that moves within the allowed speed limit. If the lane crossing speed is changed to 40 km/h, what is the minimum time, in minutes, for a vehicle to traverse it, if within the speed limit?
a) 22.5 minutes
b) 16 minutes
c) 30 minutes
d) 10 minutes
e) 45 minutes
Template: Letter a
Resolution:
First, we need to calculate the length of this track, for that, we will use the formula of the average speed:
Now that we know the length of the avenue, it is possible to determine the time needed to cross it, here's how:
To find the crossing time with the new speed limit, we had to multiply the time, given in hours, by 60, since each hour has 60 minutes.
See too: 8 Physics Formulas to Take the Enem Nature Science Test
Example 2) Two-thirds of a 600 km journey is covered at an average speed of 60 km/h. For the trip to be completed, with an average speed of 80 km/h, how long will the rest of it need to be covered?
a) 2 h and 30 minutes
b) 3 h and 20 minutes
c) 4 h and 10 minutes
d) 5 h and 40 minutes
e) 6 h and 15 minutes
Template: Letter B
Resolution:
According to the statement, two thirds of a 600 km (400 km) trip were covered with an average speed of 60 km/h. In this sense, let's determine the duration of this journey:
Once you know the duration of the journey, you can determine the total time of the trip, since the route of 600 km must be traversed with average speed of 80 km/h. This maximum time must be:
Through this calculation, we found that for maintain an average speed of 80 km/h, the trip should be done in a time of up to 30/4 h. After that we calculate the difference between the total time of the trip and the time spent during the initial two-thirds of the trip, and we find the total of 200 minutes. We then multiply the result, measured in hours, by 60, resulting in a remaining time of 3 hours and 20 minutes.
Know more: Light: what it is made of and everything else you need to know about it!
Average Scalar Speed Summary
- Average speed is calculated by dividing the total distance and the time interval in which a body has described a movement.
- Unlike average speed, in average scalar speed it is not necessary to take into account the direction and direction of movement.
- Like average speed, average speed can be measured in meters per second or kilometers per hour.
Also access:Newton's Laws: Formulas and Solved Exercises
Solved exercises on average scalar speed
Question 1) (G1 - CPS) Consider that Roberto, in his 2000 m walks to maintain his physical fitness, develops an average speed of 5 km/h. The time taken to cover this distance is:
a) 12 min
b) 20 min
c) 24 min
d) 36 min
e) 40 min
Template: Letter C
Resolution:
First we need to convert the walking distance to kilometers. As we know, each kilometer is 1000 m, so the distance covered is equal to 2 km. Then just use the formula for the average speed and multiply the result by 60, since each hour is 60 minutes long.
According to the calculation, the time needed for Roberto to walk is 24 minutes, corresponding to alternative c.
Question 2) (PUC-RJ 2017) A car travels at 100 km/h for 15 minutes and then lowers its speed to 60 km/h, traveling 75 km at that speed. What is the car's average speed for the total journey, in km/h?
a) 80
b) 75
c) 67
d) 85
e) 58
Template: Letter C
Resolution:
In order to solve the exercise, we need to know what the total distance traveled was and divide it by the total time span of the trip. In this way we will first find out what is the distance covered in the first 15 minutes (0.25 h) of travel, then we will calculate how long it took to travel 75 km at a speed of 60 km/h. Check out:
Based on the previous calculation, we found that the vehicle traveled 25 km in the first stretch and that the second stretch lasted about 1.25 h (5/4 h). Thus, the total distance covered and the total travel time are equal to, respectively, 100 km and 1.5 h.
Based on the calculations made, we find that the average speed of the mobile is approximately 67 km/h, so the correct alternative is the letter c.
Question 3) (UEA 2014) With approximately 6500 km in length, the Amazon River competes with the Nile River for the title of the longest river on the planet. Suppose that a drop of water that crosses the Amazon River has a speed equal to 18 km/h and that this speed remains constant throughout the course. Under these conditions, the approximate time, in days, that this drop would take to travel the entire length of the river is:
a) 20
b) 35
c) 25
d) 30
e) 15
Template: Letter e
Resolution:
To calculate the time, in hours, for the drop of water to travel across the river, we must use the formula of average speed. Watch:
After we have found the time in hours, we divide the result by 24, as we want to determine the approximate number of days it takes this drop to cross the river. |Therefore the correct alternative is the letter e.
By Rafael Hellerbrock
Physics teacher
Source: Brazil School - https://brasilescola.uol.com.br/fisica/velocidade-escalar-media.htm
