quan sát dòng nước chảy chậm từ vòi nước xuống dưới, ta thấy nước bị thắt lại tức là ở gần vòi tiết diện dòng nước lớn hơn tiết diện phía dưới, tại sao?

Simple machines can a. increase force only b. decrease force only c. increase or decrease force

Samir watches a 100-minute movie on his spaceship. maria's spaceshipe flies in the same direction as samir's spaceship but she observes his move to last 125 minutes and his spaceship to be 40 m long. how long does samir observe his own spaceship to be? according to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does marias voyage take according to samir?

The air that we breath is made mostly of which gaseous molecule