If your arm has been twisted it means that someone has done a great job of convincing you to do something you might not have wanted to to do. 某人很好地说服了你去做一些你可能不想做的事情。
“Jake, you should really come to the party tonight!” “You know I can’t, I have to hit the books (study).” “You have to come! It’s going to be so much fun and there are going to be lots of girls there. Please come?” “Pretty girls? Oh all right, you’ve twisted my arm, I’ll come!”
Close enough to touch, either literally or hypothetically. Easily attainable. Can you pass me that book over there? It’s within arm's reach of you. Once I found out I had an A in Chemistry, I knew that 4.0 GPA was within arm’s reach. 触手可及