I think there is an error in EK 30min In Class Exam Lect 3 #57. The question asks "how does friction between the 0.1 kg mass and the table in experiment 2 affect the results of the experiment?" I think the answer should be that the tension in the string is decreased by friction. But the solution says that the tension should increase because friction, being the force opposing the direction of tension, should increase the tension. Can someone confirm my speculation please? If the answer for this question should be increase, can someone explain the reason? I don't think the EK solution explains well. Many thanks.