mà x = -2 đang hướng về vtcb

A= 12/2 = 6cm

T = t/n = 62,8/20 = 3,14 = π s

w = 2π/T = 2π/π = 2 rad/s

v²= w²(A²- x²)

=> v² = 4 . 32
=> v = +-8√2 cm/s.

mà x = -2 đang hướng về vtcb

=> v = 8√2 cm/s

a = -w² . x

=> a = -4 . (-2)

=> a = 8cm/s²

w = 2π/T = π/2 rad/s.

A= 48/6 = 8cm.

t =0 vật đi qua vtcb

=> v < 0

x = AcosP

=> cosP = 0

=> P = +- π/2

mà vật theo chiều âm

=> v = π/2

ptdđ: 8cos(π/2t + π/2)cm

In this era, screen time has become a major part of young individuals' lives. While technology does offer many advantages, I believe that parents should limit their children's screen time to protect their health and support their development. Firstly, too much screen time can cause problems with school and health. Many teens tend to spend hours watching online videos, scrolling through social media, or playing games. This not only leaves them with a little time for homework but also make it hard for them to concentrate. Secondly, too much screen time can negatively effect affect teenagers’ health. It can damage eyesight, reduce sleep quality and cause weight gain due to lack of physical activities.

On the other hand, educational games and videos can teach valuable skills and knowledge, and not all screen time is harmful. However, without parent's guidance, teenagers may choose the wrong content on their own. So parental involvement is still necessary. Moreover, I am concerned about the generation gap might be widen due to strict rules. Teens may feel like they are misunderstood, which can lead to conflict between parents and children. To address this problem, parents should explain their reasons clearly and involve teenagers into setting screen time limits.

In conclusion, while screen time can bring many benefits if used correctly, strict limits are necessary to protect teenagers' health and help them with their development.