How do I match the animation velocity for clips of different durations?

[Anton5C11]

I have two different clips, which have a different duration, but both should have the same scale animation. One of the clips is going from 100% scale to 105.5% scale, the keyframe interpolation method is set to linear. If I look inside the graph editor, I can see that the speed is 1.50% per second. 

Now I want the second clip to have the same speed, however, it has a different duration. The question is following: is there any function in After Effects that will set the end keyframe's property of my second clip so that it has the same rate of 1.50% per second? Basically, is there any way to pick up this value for clips of different durations without having to calculate these values yourself?

[David Arbor]

While looking at the Speed Graph, you can double-click on the first keyframe and set the Outgoing Velocity to 1.5%, then double-click on the second keyframe and set the Incoming Velocity to 1.5%

[Anton5C11]

Thank you. I've just done it, but it didn't solve the problem. The second animation still has the same value, which is 1.15% per second. Take a look at the snapshot please.

[David Arbor]

Did you make sure to set the Outgoing Velocity of the first keyframe and the Incoming Velocity of the second keyframe, not the other way around? This screenshot by itself doesn't tell me a lot. What does the animation of the two actually look like to you?

[Anton5C11]

You see, I have 4 different keyframes for the scale property.

The first pair has velocity of 4.5% per second, it goes from 100% to 103% scaling, and the duration between the two keyframes is 10 frames.

While the second one has velocity of 1.5% per second (this is my target value), it goes from 100% to 105.5% scaling, and the duration between the two keyframes is 60 frames.

I want both keyframe pairs to have the same velocity value of 1.5% per second. How do I need to adjust the first pair's percentage of the scale property to match the velocity of 1.5% between the two keyframes, while not changing their duration?

[David Arbor]

This is more complicated than the two keyframes it sounded like you originally had. Sometimes you have to eyeball things knowing that it's not possible to achieve the same velocity for different durations without easing. At some point you won't be able to do what you want to do simply because of math. If you have a fixed value you want to scale and a fixed duration you want it to happen in, the variable value must be velocity. If you want 1.5%/sec then have to use an easing curve, but that means your velocity will only be 1.5%/sec for a short period of time. This is a really good example of how to think about the speed graph in a different way: https://www.instagram.com/p/B9hG2KqjVV8/

Another way to put this is: (I'm assuming you're working in a 30fps comp) if you want a 3% scale to happen in 10 frames, how can it only scale up at 1.5%/sec? That means it would take 2 seconds to scale. So, 4.5%/sec means it will take 1/3 of a second to get to 103%, which is your 10 frames. 

[Warren Heaton]

Copy and paste the Scale keyframes from the shorter clip to the longer clip and then apply a loopOut('Offset') Expression to the Scale parameter of the longer clip.