Put an object with a mass of 1kg on a horizontal plane, use 8N horizontal pulling force to make the object move from rest, the dynamic friction coefficient between the object and the horizontal plane is 0.2, and remove the pulling force when the object moves for 2S. (G is taken as 10m / S2) calculate: (1) the kinetic energy of the object at the end of 2S. (2) the maximum distance that the object can slide forward on the water plane after 2S

Put an object with a mass of 1kg on a horizontal plane, use 8N horizontal pulling force to make the object move from rest, the dynamic friction coefficient between the object and the horizontal plane is 0.2, and remove the pulling force when the object moves for 2S. (G is taken as 10m / S2) calculate: (1) the kinetic energy of the object at the end of 2S. (2) the maximum distance that the object can slide forward on the water plane after 2S

(1) According to Newton's second law: f-f = ma solution: a = f − FM = 8 − 0.2 × 101m / S2 = 6m / S2, then the kinetic energy of the object at the end of 2 seconds is EK = 12mv2 = 12 × 1 × (6 × 2) 2J = 72j (2) according to the kinetic energy theorem, from rest to stop, then f × 12at2 − f (12at2 + x) = 0 − 0 & nbsp; solution: x = 36