Leather part for their skins. Kangaroo leather is used to make items that must be strong and flexible. It is the material most commonly used in bullwhips. Some motorcyclists favor kangaroo leather for motorcycle leathers because of its light weight and abrasion resistance. Kangaroo leather is also used for falconry jesses, soccer footwear, and boxing speed bags. Although originally raised for their feathers in the 19th century, ostriches are now more popular for both meat and leather. Ostrich leather has a characteristic "goose bump" look because of the large follicles where the feathers grew. Different processes produce different finishes for many
Momentum exchange tether than the orbital velocity of the tether and the upper endpoint is moving faster. The word is a portmanteau derived from the words "rotor" and "elevator". If the tether is long enough and the rotation rate high enough, it is possible for the lower endpoint to completely cancel the orbital speed of the tether such that the lower endpoint is stationary with respect to the planetary surface that the tether is orbiting. As described by Moravec, this is "a satellite that rotates like a wheel". The tip of the tether moves in approximately a cycloid, in which it is momentarily