PHYS172_F23_Exam2-PRACTICE

PHYS 172 EXAM 2 PRACTICE (150 Points) FALL 2023 3 Problem 03: [10 points] A liquid of mass, ? ? , specific heat, 𝐶 ? and initial temperature, 𝑇 ? is poured into a pan of mass mass, ? 𝑃 , specific heat, 𝐶 𝑃 and initial temperature, 𝑇 𝑃 . Which of the equations below should you solve to calculate the final equilibrium temperature, 𝑇 ?𝑖??? of the water and the pan? A) ? ? 𝐶 ? (𝑇 ?𝑖??? − 𝑇 ? ) + ? 𝑃 𝐶 𝑃 (𝑇 ?𝑖??? − 𝑇 𝑃 ) = 0 B) ? ? 𝐶 ? (𝑇 ?𝑖??? − 𝑇 ? ) + ? 𝑃 𝐶 𝑃 (𝑇 𝑃 − 𝑇 ?𝑖??? ) = 0 C) ? ? 𝐶 ? (𝑇 ? − 𝑇 ?𝑖??? ) + ? 𝑃 𝐶 𝑃 (𝑇 ?𝑖??? − 𝑇 𝑃 ) = 0 D) ? ? 𝐶 ? (𝑇 ?𝑖??? − 𝑇 ? ) − ? 𝑃 𝐶 𝑃 (𝑇 ?𝑖??? − 𝑇 𝑃 ) = 0 E) None of the above

PHYS 172 EXAM 2 PRACTICE (150 Points) FALL 2023 6 Problem 07: [8 points] Three uniform objects -- circular disk, sphere, and hoop -- all have the same mass and radius. They are held initially at rest at the top of an inclined plane. You let go and the objects roll down the incline without slipping. Which will reach the bottom first ? Note: ? ℎ??? = ?? 2 , ? ?𝑖?? = 1 2 ?? 2 , ? ?ℎ??? = 2 5 ?? 2 A) Disk B) Sphere C) Hoop D) All equal E) There is not enough information

PHYS 172 EXAM 2 PRACTICE (150 Points) FALL 2023 9 Problem 10: [10 points] Three students present statements about how to find the speed ? ? at which the block is launched into the air at the top of the spring. Which is correct? Amy: You choose the block as the system and Earth and spring as the surroundings and your equation is: ( 1 2 ?? 0 2 − 0) = −?𝑔(? 0 − ?) + 1 2 𝑘 ? (? 0 − ?) 2 Beth: You choose the block and spring as the system and Earth as the surroundings and your equation is : ( 1 2 ?? 0 2 − 0) + (0 − 1 2 𝑘 ? (? 0 − ?) 2 ) = −?𝑔(? 0 − ?) Cathy: You choose the block, spring, and Earth in the system, and nothing in the surroundings, then your equation is: ( 1 2 ?? 0 2 − 0) + ?𝑔(? 0 − ?) = 1 2 𝑘 ? (? 0 − ?) 2 A) Amy is correct, but Beth and Cathy are wrong. B) Beth is correct, but Amy and Cathy are wrong. C) Cathy is correct, but Amy and Beth are wrong. D) Both Amy and Beth are correct, Cathy is wrong. E) None of them is correct. Problem 11: [10 points] What is the maximum height, ℎ ??? achieved by the block before it starts to come down again? A) ℎ ??? = ? 0 2 2? B) ℎ ??? = ? 0 2 ? C) ℎ ??? = 2? 0 2 ? D) ℎ ??? = 3? 0 2 ? E) None of the above

PHYS 172 EXAM 2 PRACTICE (150 Points) FALL 2023 12 Problem 15: [10 points] Four objects, each of mass m are attached to a disk of mass ? and radius 𝑹 as shown. Each object is at a distance 𝒃 from the axis of the disk. The system is initially at rest on a frictionless flat surface. A string is would around the disk and such that when the end of the string pulled with a constant force ? , the disk both rotates and translates. When the end of the string is pulled a distance ? + ? , the center of mass of the disk (and 4 masses attached to it) has translated a distance ? . What is the angular speed , 𝝎 of the system at this instant? Note: The moment of inertia ? ?𝑖?? = 1 2 ?? 2 and ? ??𝑖?? ???? = 𝑚𝑏 2 A) 𝜔 = √ 4𝐹(?+?) 8?? 2 +?𝑅 2 B) 𝜔 = √ 4𝐹? 8?? 2 +?𝑅 2 C) 𝜔 = √ 4𝐹? 8?? 2 +?𝑅 2 D) 𝜔 = √ 2𝐹? 4?? 2 +?𝑅 2 E) 𝜔 = √ 2𝐹? 4?? 2 +?𝑅 2