lí do chọn đề tài nghiên cứu: vận dụng tư tưởng Hồ Chí Minh về đại đoàn kết dân tộc trong giai đoạn hiện nay

Aspring is used to stop a 50-kg package which is moving down a 20º incline. the spring has a constant k = 30 kn/m and is held by cables so that it is initially compressed 50 mm. knowing that the velocity of the package is 2 m/s when it is 8 m from the spring and neglecting friction, determine the maximum additional deformation of the spring in bringing the package to rest.

Suppose astronomers built a 140-meter telescope. how much greater would its light-collecting area be than that of the 10-meter keck telescope? express your answer using two sign

What do we mean by the event horizon of a black hole?