Understanding Relative Speed
What do you already know about relative speed?
Items in this lesson
What do you already know about relative speed?
Units
In physics we use units as we do in all science lessons, when it comes to motion we use the following
M/s = metres per second
Km/h = Kilometre per hour
Sometimes we will have to convert time from minutes to seconds or hours to seconds
What units do we use when calculating relative velocity?
Inches per minute
Meters per second
Kilometers per hour
Miles per hour
Concept of Relative Speed
Relative speed is the speed of one object as observed from another object, calculated as the difference between their individual speeds when they are moving in the same direction.
Calculating Relative Speed
When two objects are moving in the same direction, their relative speed is the difference between their speeds.
Equation:
Relative speed = Fastest speed - Slowest speed
Real-life Application of Relative Speed
Understanding relative speed helps in scenarios like overtaking in traffic or calculating the speed of a moving object from a stationary point.
Definition List
Relative Speed: The speed of one object as observed from another object, calculated as the difference between their individual speeds when they are moving in the same direction.
Fastest Speed: The higher speed among two objects being compared. Slowest Speed: The lower speed among two objects being compared.
What is the equation for relative motion of two objects moving in the same direction?
Relative Speed = Speed of Object 1 * Speed of Object 2
Relative Speed = Speed of Object 1 - Speed of Object 2
Relative Speed = Speed of Object 1 + Speed of Object 2
Relative Speed = Speed of Object 1 / Speed of Object 2
If Car A is moving at 60 mph and Car B is moving at 70 mph in the same direction, what is their relative speed?
Relative Speed = 70 mph
Relative Speed = 10 mph
Relative Speed = 130 mph
Relative Speed = 60 mph
When two objects are moving in the same direction, what happens to their relative speed if their individual speeds increase?
The relative speed becomes zero
The relative speed remains the same
The relative speed increases
The relative speed decreases
When two bodies are moving in opposite directions, what is the relative velocity between them?
Product of the velocity of the bodies
Difference in velocity of the bodies
Average of the velocity of the bodies
Sum of the velocity of the bodies
If two bodies are moving in the same direction, what is the relative velocity between them?
Product of the velocity of the bodies
Sum of the velocity of the bodies
Average of the velocity of the bodies
Difference in velocity of the bodies
What is the relative velocity when two bodies are moving in opposite directions and one has a velocity of 5 m/s and the other has a velocity of 3 m/s?
3 m/s
2 m/s
8 m/s
5 m/s
Relative speed in opposite directions
When two bodies are moving in opposite directions, relative velocity between them is equal to sum of the velocity of bodies. But if the bodies are moving in same direction their relative velocity is equal to difference in velocity of the bodies
Two cars are moving in opposite directions. Car A is traveling at 60 mph and car B is traveling at 40 mph. What is the relative speed of car A with respect to car B?
40 mph
20 mph
60 mph
100 mph
A boat is moving at 8 m/s in a river flowing at 2 m/s. What is the relative velocity of the boat with respect to the river's bank?
2 m/s
10 m/s
4 m/s
6 m/s
Two cyclists are riding in the same direction. Cyclist A is traveling at 15 km/h and cyclist B is traveling at 12 km/h. What is the relative speed of cyclist A with respect to cyclist B?
12 km/h
3 km/h
9 km/h
27 km/h
If one body is moving at 10 m/s and the other is moving at 5 m/s in the same direction, what is their relative velocity?
10 m/s
3 m/s
5 m/s
15 m/s
What is the relative velocity when two bodies are moving in opposite directions and one has a velocity of 8 m/s and the other has a velocity of 2 m/s?
3 m/s
10 m/s
5 m/s
6 m/s
What do you now know about relative velocity/speed?
Write down 3 things you learned in this lesson.
Write down 2 things you want to know more about.
Ask 1 question about something you haven't quite understood yet.
