Câu 1. Trường hợp nào dưới đây không phải là vật sáng? A. Chiếc bút chì đặt trên bàn giữa ban ngày.

B. Chiếc bật lửa rơi giữa sân trường lúc trời nắng.

C. Mặt Trời.

Identify the theory that can be used to explain each phenomenon. answers diffraction: wave theory interference: wave theory reflection: both particle and wave theories refraction: both particle and wave theories

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.

Considering only the earth's rotation, determine how much later the asteroid would have had to arrive to put the explosion above helsinki at longitude 25˚ e? this would have obliterated the city.