Hai người đi xe đạp cùng chd thẳng đều từ a đến b .Ng 1 xuất phát lúc 6h vs vận tốc v1 =6km/h. Ng 2 xuất phát lúc 6h30' vs vạn tốc v2 =12km/h .A) xác định khoảng cách giữa hai người đó lúc 7h30'.B) 1 ng thứ ba cũng đi xe đạp từ a đến b vs vận tốc ko đổi v3 nhưng xuất phát lúc 7h .Khoảng thời gian giữa hai lần gặp nhau của ng thứ ba vs ng thứ nhất và ng thứ hai là ∆t=54' .Xác định vận tốc v3 của ng thứ ba

Which of the following represents an upright image? a. -do b. +m c. -m d. +do

A23 kg log of wood begins from rest, 300 m up a sluice (a water track used to transport logs, think of it as an inclined plane with negligible friction) inclined at 20° to the horizontal. after it reaches the flat waterway at the bottom it collides elastically with a 100 kg block of wood initially at rest near the base of the incline. (a) how long does it take the 23 kg log to travel down the incline? (b) what is the speed of the 23 kg log at the bottom of the incline? (c) what are the velocities of both blocks of wood after the collision? (d) what is the total kinetic energy before the collision? (e) what is the kinetic energy of the 23 kg log after the collision? (f) what is the kinetic energy of the 100 kg block of wood after the collision? (g) what is the total kinetic energy after the collision? (h) compare the total initial and total final kinetic energies. is this consistent with what you would expect for elastic collisions? explain!

Arotating space station is said to create “artificial gravity”—a loosely-defined term used for an acceleration that would be crudely similar to gravity. the outer wall of the rotating space station would become a floor for the astronauts, and centripetal acceleration supplied by the floor would allow astronauts to exercise and maintain muscle and bone strength more naturally than in non-rotating space environments. if the space station is 200 m in diameter, what angular velocity would produce an “artificial gravity” of 9.80 m/s^{2} 2 at the rim?