In the last video, we figured out the absolute minimum
speed in order to stay on the circular path right over here especially near the top
was 27.6 km/h
What I want to do in this video is
I just clipped out the parts where he's actually on the loop de loop
and I want to figure out his average [speed]
So I'm going to use the video editor right here
to time how long it takes to complete the loop de loop
And then we can use that and we know about the circumference of this loop de loop
and we're going to assume that it is perfectly circular for our purpose
although it looks like it's a little bit egg-shaped in reality or elliptical
For our calculation, we're going to assume that it's perfectly circular
I'll leave it to you to think about how it would change
if you had an elliptical shape like this
So anyway, let's watch the video again
Remember this is from fifth gear which shows on Channel 5 in United Kingdom
So there you go
Let's watch it again. It's fun to watch. There you go
And right over here, we have a little timer for my video editor
And this right over here is in seconds and I was corrected on a earlier video
This right over here is not in hundredth of seconds. This is in frames
And there's 30 frames per second
So it starts at 0 seconds 0 frames
and then when we play it, it goes to 2 seconds and 14 frames
There's 30 frames per second
So it's 2 and 14/30 of a second. It's how long it takes the car to do the loop
So 1 second, and then 2 seconds, 2 and 14/30. So almost 2.5 second
So let's write that down
So the time required to do the loop de loop is roughly 2 and 14/30 seconds
And what is the distance that it travels?
If we assume that this thing is circular although it looks like it's a little bit egg-shaped
if we assume that it is circular
then the distance traveled is the circumference of the circular loop de loop
The circumference is 2 pi times the radius which is equal to 2 pi
and in the previous video, we figured out the radius was 6 m
So it's 2 pi times 6 m which is equal to 12 pi meters
If you wanted to figure out its average speed--
the velocity is constantly changing because the direction is changing
but the magnitude of the velocity--
if we wanted to figure out the average magnitude of the velocity or the average speed
the total distance traveled is 12 pi meters
divided by the time required to travel the 12 pi meters
so that is 2 and 14/30 seconds
Now let's get our calculator out to actual calculate that value
So we're going to have the distance 12 pi m divided by
2 + 14/30 just to get the exact value
And then this gives us in meters per second
15.3 m/s
So the average speed is approximately 15.3 m/s
which is almost twice as fast as the minimum speed we figured out
because you want that margin of safety
and you want to be able to have some traction with the road
Although you don't want to go too fast, because then the G force is going to be too big
then this--maybe we'll talk about that in the future video
I'll just relate this into kilometers per hour. Let's figure out what that is
I want to use the calculator here
So that's in the meters per second
Let's figure out how many meters per hour by multiplying it by 3600 seconds per hour
So that's how many meters per hour, and divide it by 1000 which you can see right over there
that is 55 km/h
If you want to do it in miles, it's rough approximation, divide it by 1.6
It's about 35 mph give or take or 55 km/h
So this is approximately 55 km/h
So the driver here luckily they did the physics ahead of time
and he had the margin of safety
He was well in excess of the minimum velocity just to maintain the circular motion
So he probably has some nice traction with the track up here