Part A A force F acts in the forward direction on a cart of mass m. A friction force f opposes this motion. Use Newton's second law and express the acceleration of the cart. Express your answer in terms of the variables F, f, and m. VO AEd a= Submit Request Answer V Part B If the cart's mass is 4.2 kg , the applied force is 12.4 N , and the friction force is 6.8 N , find the cart's acceleration. Express your answer to two significant figures and include the appropriate units. HA a = Value Units Submit Request