An object travels from a point X to another point Y in 10 s. The distance between them is 30 m. It travels again from Y to Z and covers 40 m. The average speed of the object during the whole journey is 2 m/s. How long the object takes to travel from Y to Z?​

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.