In the second video lecture there's an example about the pumpkin drop and I'm a little confused. First, where did he get the 5t^2? Is he rounding the constant for acceleration due to gravity? Second, when he says "speed" does he mean velocity? I got a little confused because speed is usually defined as the absolute value of velocity, but he wrote Avg Speed = -20m/s.
I just want to make sure I know what lingo is being used.

Question

In the second video lecture there's an example about the pumpkin drop and I'm a little confused.  First, where did he get the 5t^2?  Is he rounding the constant for acceleration due to gravity?  Second, when he says "speed" does he mean velocity?  I got a little confused because speed is usually defined as the absolute value of velocity, but he wrote Avg Speed = -20m/s. 
 I just want to make sure I know what lingo is being used.

anonymous · Answer

I haven't seen this video but you are correct: speed=lvl>0. And yes the assumption would be that g is approx 10 so 1/2g=5

anonymous · Answer

Ok, thanks, I just wasn't sure because in every calc and physics class I've ever had we've used g=9.8, and my teachers were always really big sticklers about when you use the term speed versus velocity.  And this being MIT, I figured that they would be even more intense than where I was, so I started to question if I was actually remembering correctly.