Vật 1 được nối với vật 2 bằng dây không dãn. m 1   =   m 2   =   2 k g . Kéo vật m 1 bằng lực 10N theo phương ngang là hệ vật chuyển động với gia tốc 2m/ s 2 . Lấy g = 10m/ s 2

Hệ số ma sát của mặt sàn là:

A. 0,02

B. 0,0025

C. 0,05

D. 0,015

Read the following passage and answer the questions below.

Everyone wants to reduce pollution. But the pollution problem is as complicated as it is serious. It is complicated because much pollution is caused by things that benefit people. For example, exhaust from automobile provides transportation to millions of people. Factories discharge much of the material that pollutes the air and water, but factories give employment to a large number of people.

Answer the questions.

Why is the pollution problem complicated?