How do we measure speed?
how to determine the distance between two points using a map;
that vehicles and people move at different speeds.
explain what movement is
define distance and velocity
If we know the distance we have travelled and the time in which it took, then we can calculate the velocityvelocity of our movement. Just divide the distance travelled by the timetime taken. The speed tells us, what distancedistance we travel in a given time.
A unit of speed is meters per second (m/s). However, in everyday life we give the speed in kilometers per hour (km/h), because it is difficult to precisely measure the distance that we travel in one second. If you compare the speeds of different objects, e.g. two cars, they should be given in the same units. So what should be done if the speed of one of them is given in m/s, and the other in km/h? It’s simple: remember that a kilometer is 1000 m and an hour is 3600 s. So if you're riding a bike at 18 km/h, it means your speed is:
= = 18/3,6 = 5 m/s.
If this calculation seems too complicated – you're absolutely right. There is more natural way to do this.
If we want to change the speed from km/h to m/s, we divide it by 3.6. If we have the speed given in m/s, and we want to change it in km/h, we multiply it by 3.6.
Measuring the speed of walking and running.
a tape measure,
a stopwatch,
a second person to help.
Using a tape measure, one person should measure a distance of 60 m.
Let each partner travel the distance twice– the first time at normal walking speed and the second time running.
When one person walks or runs, the other person has to measure time.
Knowing the distance and the time taken to walk and run it, calculate the speed of both.
Knowing the distance and the time it took to travel it, you should calculate the speed in meters per second as well as kilometers per hour.
The driver of a car was driving from Wroclaw to Katowice via the A4 motorway. He travelled this route in 2.5 hours. The return journey took him 30 minutes less. In both cases he drove continuously. Which of the following are true?
- The driver from Katowice to Wroclaw was driving at a higher speed than from Wroclaw to Katowice.
- The driver from Katowice to Wroclaw was driving at a lower speed than from Wroclaw to Katowice.
- The driver from Wroclaw to Katowice was driving at the same speed as from Katowice to Wroclaw.
If a car covers 200 meters within 50 seconds, it means that it is moving at the speed of:
- 4m/s
- 40 m/s
- 0,25 m/s
- 25m/s
Summary
Movement is the motion of one thing relative to another thing.
Knowing the distance travelled and the time it took to complete, we can calculate the velocity of an object.
Give examples of types of motion. Indicate at least two examples of uniform motion and two examples of non‑uniform motion.
Keywords
velocity, distance, time
Glossary
prędkość – stosunek drogi pokonanej przez obiekt do czasu, w jakim została ona pokonana; wyrażamy ją w metrach na sekundę lub kilometrach na godzinę.
droga – odległość, jaką pokonuje poruszające się ciało; mierzymy ją w metrach lub w innych, mniejszych albo większych jednostkach.
czas – wielkość fizyczna określająca kolejność zdarzeń oraz odstępy między zdarzeniami zachodzącymi w tym samym miejscu. Pojęcie to było również przedmiotem rozważań filozoficznych.