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    <blockquote> <p>def update(self):</p> <pre><code> self.speed.y -= GRAVITY displacement = Vec2d( self.direction.x * self.speed.x, self.direction.y * self.speed.y ) self.pos += displacement </code></pre> </blockquote> <p>You call Dot.update() 50 times every second. The equation you're using, </p> <pre><code>delta v_y = - g #* (1 second) </code></pre> <p>represents the change in velocity <strong>every second</strong>, but it gets called 50 times every second. This means your velocities will lose <code>50*GRAVITY m/s</code> ever second and this is why you are forced to make your gravity so weak. </p> <p>So, I would recommend adding <code>time_passed</code> as an argument for <code>Dot.update</code>, and change the speed changing statement to</p> <pre><code>def update(self, time_passed): self.speed.y -= GRAVITY * time_passed/1000. #time converted from millisecond to seconds </code></pre> <p>This will make the units more intuitive. Switch <code>GRAVITY</code> back to 10 and use realistic velocities. </p> <p><strong>EDIT:</strong></p> <p>Additionally, the displacement vector also needs to contain time, or else the displacement will depend on FPS. If you have <code>x</code> frames per second, then each update occurs after <code>t = 1000/x</code> milliseconds. This is the amount of time Dot spends "moving" in each update. Think about how we approximate Dot's motion; it gets an update, calculates its new velocity and travels at that speed for <code>t</code> seconds. However, in your implementation, the displacement vector is independent of time. Change the update method to be something like:</p> <pre><code>def update(self, time): time /= 1000. self.speed.y -= GRAVITY * time displacement = Vec2d( self.direction.x * self.speed.x * time, self.direction.y * self.speed.y * time ) self.pos += displacement </code></pre> <p>Now, according to kinematics, we'll get something like </p> <pre><code>max height = v0**2 / 2g </code></pre> <p>so initial velocities of 10-20m/s will only produce max heights of 5-20m. If you don't want to work with velocities of 50-200m/s, then you could add a scaling factor in the displacement vector, something like </p> <pre><code> displacement = Vec2d( self.direction.x * self.speed.x * time * scaling_factor, self.direction.y * self.speed.y * time * scaling_factor ) </code></pre>
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    1. COThanks alot for your answer! This makes a lot of sense now. One of those (facepalm) moments ;). One thing I noticed, however, is that on changing the amount of frames per second, there is a difference on how high Dot rises toward the ceiling (50: almost touches the top; 25: just below half the height of the window; 10: not even bottom third before descent). How would I adjust this to have the distance travelled independent from the Frames per second?
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    2. COYeah, that's a good point. Check out the edit.
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    3. COFantastic! With the scaling_factor you even answered a question, I was working on, but haven't asked ;) Great stuff! Game Physics 101. Thanks a lot!
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