After a brief mention of the formula for momentum, I moved to cover Newton's three laws as formulated from a momentum perspective. Momentum unites the first two laws nicely into variations of the same formula. I rearranged the tables in A101 and rode my RipStik while a ball balanced loosely in my outstretched hand. I collided with a table on one side of the room, and the ball kept on going. Not as vivid as the outdoor demo I did last spring under the solar panels. The greater speed made a lot of difference. Then I used the new clothes line rope to hold 8 kg up. I used this to pull me. The 50 cm drop that the table top provided was insufficient to gain much speed. Not much better than 65 cm/s². Still, that provided the numbers I needed to work out what my acceleration must have been. Note that measuring speed post-acceleration, while not ideal, is far easier than timing the acceleration directly. One is rather busy getting accelerated, thoughts of timing are secondary. ...