I have a question: Al and Bert stand in the middle of a large frozen lake (frictionless surface). Al pushes on Bert with a force of 20 N for 1.2 s. Bert's mass is 114 kg. Assume that both are at rest before Al pushes Bert. (a) What is the speed that Bert reaches as he is pushed away from Al? wrong check mark m/s (b) What speed does Al reach if his mass is 72 kg? m/s For part A I did F = MA 20N = 114kg * A A = .18 m/s^2 .18 m/s^2 * 1.2s = .21 m/s Is this correct? As for Part B Since 20N is applied to Bert, 20N is also applied to Al from Newton's 3rd law. So F = MA 20N = 72kg * A A = .18 m/s^2 .28 m/s^2 * 1.2s = .33 m/s Is this correct? Also another question A person in an elevator is holding a 11 kg block by a cord rated to withstand a tension of 157 N. When the elevator starts up, the cord breaks. What was the minimum acceleration of the elevator? Use Newton's Second Law of Motion F=ma therefore 157/11 = a = 14.27 m/s squared This came out to be wrong, how come?