obstacle、barrier、obstruction、bar与hindrance这些名词均含“障碍（物）”之意。

obstacle : 指在达到目的或前进的过程中必须消除或绕过的障碍物，也指起阻碍作用等情况。

• A lack of qualifications can be a major obstacle to finding a job.
  学历不足可能成为谋职的主要障碍。
• So far, we have managed to overcome all the obstacles that have been placed in our path.
  至此，我们已设法排除了设置在道路上的一切障碍。

barrier : 常指临时的或者可能跨越的障碍。

• The crowd had to stand behind barriers.
  人群只好站在障碍物后面。
• Show your ticket at the barrier.
  请在验票处出示车票。

obstruction : 常既指具体的障碍又可指抽象或喻意上的阻碍。

• the obstruction of justice
  妨碍司法公正
• He was arrested for obstruction of a police officer in the execution of his duty.
  他因妨碍警察执行公务而被逮捕。

bar : 既可指阻止进出或通过的栅栏一类的障碍物，也可用于抽象意义障碍。

• At that time being a woman was a bar to promotion in most professions.
  那时在大多数职业中，身为女性就是晋升的障碍。

（拓展学习：熟词僻义 | bar 是一个什么介词？）

hindrance : 指妨碍他人进步或做事的人或物。

• To be honest, she was more of a hindrance than a help.
  说实在的，她没帮上忙，反而成了累赘。
• The high price is a major hindrance to potential buyers.
  价格高是使潜在买主却步的主要因素。