Physics Results In A Physical Reaction

(I am in ninth grade and my sister is in eighth. My sister is struggling in school, so our parents have asked me to tutor her in physics. We are sitting in her room and I am trying to go over her homework with her, but she is refusing to stay on task.)

Me: “Unit conversions are not that hard. Just make sure the unit you want to cancel is opposite to the conversion multiple so the units cancel diagonally. It’s just like… like multiplying fractions…”

(I notice her not paying attention again. She is spitting spit balls through a straw around her room.)

Me: *fed up and out of patience, I grab the straw and yank it from her hand* “Will you cut that out and stop wasting my time!?”

(As I wrestle the straw from her hand, she grabs her pen and stabs me in the knee with it. I knock her away before she can cause any real damage.)

Sister: *whining and indignant* “Owwww! You’re going to give me a bruise!”

Me: “You’re giving me a puncture wound!”

(I wasn’t asked to tutor her any more. My sister ended up in summer school… four times.)