Question
Please Answer Completely.
Directions: Carefully read each question then write your response in the appropriate section on your answer sheet. Only complete sentences will receive full credit. Imagine a hoop and a disk, each with the exact same mass and radius. The hoop and disk are rolled down the same incline from the same height. Three students argue about which will be traveling the fastest it reaches the bottom of the ramp. Assume there is no slipping. Alvin: The hoop will be traveling the fastest. Simon: The disk will be traveling the fastest. Theodore: Both the hoop and disk will be traveling the same speed. Using your knowledge of energy conservation and rotational dynamics, explain which student is correct. Be sure to include an explanation of WHY the answer you choose is the correct answer. A physics class is asked the following question on a test: "A young French woman throws a heavy lead ball into clay. The ball initially penetrated to a depth of 4 cm. If the same ball is to be thrown into the clay and penetrate to a depth of 16 cm, then how much faster must the ball be thrown?" Half of the students (Student group A) replied, "The ball must be thrown twice as fast." Half of the students (Student group B) replied, "The ball must be thrown four times as fast." The teacher explained that Student group A was correct, not Student group B. Using your knowledge of Physics, explain why Student group A was correct.
Explanation / Answer
1)Disk will travel faster, because of less moment of inertia _________________ 2) because the kinetic energy is proportional to square of velocity, so twice the velocity would result in four times the kinetic energy, hence student A is correct.