A body does a full circle of 4-meter radius in 1.5 seconds. Calculate:
a) the average speed.
b) the average velocity.
Travels a full circumference of radius r=4m.
Elapsed time Δt=1,5 s. Δt=1,5 sg.
To solve we will use the equation that establishes that average speed is the ratio of distance traveled (Δs) and the time that it takes to do it (Δt):
Looking at the equation we can see that we know how long it takes to finish (Δt = 1.5 s), but we need to know the distance traveled in this time. However, we know that it moves along a circumference and that the length of a circumference is given by the following expression:
Substituting r=4 m,
Once we know s, we can calculate the average speed with the previous equation:
The same as in the previous question
Average velocity is given by the following expression:
where is the displacement. Since the body does a full circle, once the 1.5 seconds have passed the body will be back to the starting point and there will be no displacement at all, that is, . Therefore, the average velocity vector for this case is and its magnitude will be 0. Then: