an atwood machine uses a cable drawn over a pulley to connect two or more masses. one of the masses acts as a counterbalance or counterweight to reduce acceleration because of gravity. elevators in multi-level buildings are examples of atwood machines. the counterweight in an elevator is typically the mass of the elevator plus about half of the mass of the allowable load. in an atwood's machine experiment, the larger mass is 1.8 kg and the smaller mass is 1.2 kg. a. ignoring friction, what is the acceleration of the masses? b. what is the tension in the string?