Lab-5 Energy Online (1)

P hy s i c s L a b 5 ( O n l i n e S i m u l a t i o n ) ENERGY Mechanics Unit 6 TA name: Ishaan Varshney Due Date: Student Name: Student ID: Pre-Lab Problem 1 : If we consider the Universe as an isolated system, then the total energy of universe is conserved. a) True b) False Problem 2 : If the change in the kinetic energy of a body is 64 J, its mass is 2 kg and initial velocity is 6 m/s, what is the final velocity of the body? Problem 3 : A stone of mass 2.5 kg is thrown from a height h. The change in potential energy is 735 J and the potential energy at ground level is 0. What’s h? (g=9.8 m/s.s) Problem 4 : The Energy stored in the body due to frictional force is: a) Kinetic Energy b) Potential Energy c) Thermal Energy Problem 5 : The total change in energy of a body is 1000 J. The change in mechanical energy is 580 J. What’s the change in thermal energy of the body? (Neglecting any other energy form)

P hy s i c s L a b 5 ( O n l i n e S i m u l a t i o n ) Simulation Activity #4: Energy Skate Park Simulation created by the Physics Education Technology Project (PhET) c/o The University of Colorado at Boulder http://phet.colorado.edu/ Investigating Energy Exchanges: Kinetic Energy and Gravitational Potential Energy Objective: This activity is intended to enhance your physics education. We offer it as a virtual lab online. We think it will help you make connections between predictions and conclusions, concepts and actions, equations and practical activities. We also think that if you give this activity a chance, it will be fun! This is an opportunity to learn a great deal. Answer all questions as you follow the procedure in running the simulation .

P hy s i c s L a b 5 ( O n l i n e S i m u l a t i o n ) Gravitational Potential Energy: The potential energy associated with a system consisting of Earth and a nearby particle is gravitational potential energy. If the particle moves from y 1 to height y 2 , the change in gravitational potential energy of the particle-Earth system is  U = mg(y 2 – y 1 )=mg  y Kinetic Energy: The kinetic energy is associated with the state of motion of an object. If an object changes its speed from v 1 to v 2 , the change in kinetic energy is  K = K 2 – K 1 = ½ mv 2 2 - ½ mv 1 2 Procedure: Open Energy Skate Park http://phet.colorado.edu/simulations/sims.php?sim=Energy_Skate_Park Part I: Friction Parabola Track 1. Click Reset and observe the energy bars as the skater moves back and forth. As the skater descends his kinetic energy (green) ____________ and his potential energy (blue)_________. The total energy bar_____________. -3 2. Considering the bottom of the parabola as a reference line, measure the maximum height (h) the skater climb. h = ___ -2 3. The gravitational potential energy at the maximum height is equal to _____Joules. -2 4. The skaters speed at the minimum point of the parabola is equal to ______m/s. -2 5. Change the skateboarder (say Bulldog) and repeat steps 2, 3, and 4. -3 a. h = ______ m b. gravitational potential energy = ______ Joules c. speed = _____ m/s 6. Is the law of conservation of energy affected by the mass of the skater? Yes/no. -2 7. Now click Reset and observe the Energy versus Position graph as the skater moves back and forth. Do not forget to put the reference line at the minimum point of the parabola a. Pause the simulation at the bottom of the parabola. -4 i. Kinetic energy = ______Joules ii. Potential energy = ______Joules b. Run the simulation again, and then pause it at the maximum height. -4 i. Kinetic energy = ______Joules ii. Potential energy = ______Joules 8. Apply the following settings for the simulation to answer the proceeded questions. a. Stop the simulation b. Click Reset then return skater buttons c. Adjust the coefficient of friction to one-eighth mark on the slide d. Open the Energy versus Time graph e. Run the simulation for 20 seconds 9. What are the energies at 12 seconds and 17 seconds -6 a. at 12 seconds: K = ________ J U = ________ J E th = ________ J b. at 17 seconds: K = ________ J U = ________ J E th = ________ J 10. Calculate the change and total energies -8 a.  K = ________ J  U = ________ J  E th = ________ J b. Total energy:  E =  K +  U +  E th = _________ J Part II: Double Well (Roller Coaster)

P hy s i c s L a b 5 ( O n l i n e S i m u l a t i o n ) 1. Click Reset and return skater buttons and put the reference line as shown above. Measure height of each control point from the reference line and calculate the potential (U), kinetic (K), and total (E) energies. -16 (-1 each) a. At point 1: h 1 = ___ m. U 1 = ______J K 1 = ______J E 1 = ______ J b. At point 2: h 2 = ___ m. U 2 = ______J K 2 = ______J E 2 = ______ J c. At point 3: h 3 = ___ m. U 3 = ______J K 3 = ______J E 3 = ______ J d. At point 4: h 4 = ___ m. U 4 = ______J K 4 = ______J E 4 = ______ J 2. Calculate the speeds at control points 3 and 4 using the kinetic energies result you calculated in the previous step. -4 a. The skaters speed at point 3: v 3 = _______m/s b. The skaters speed at point 4: v 4 = _______m/s 3. Now open the Energy vs position graph and read the potential (U), kinetic(K), and total (E) energies at the control points. -12 a. At point 1: U 1 = ______J K 1 = ______J E 1 = ______ J b. At point 2: U 2 = ______J K 2 = ______J E 2 = ______ J c. At point 3: U 3 = ______J K 3 = ______J E 3 = ______ J d. At point 4: U 4 = ______J K 4 = ______J E 4 = ______ J 4. Calculate the heights at each of the control points using the information from step 3. -5 a. h 1 = ____ m, h 2 = ____ m, h 3 = ____ m, h 4 = ____ m, h 5 = ____ m. 5. How the shape of potential and kinetic energies do related to the shape of the track? -4 a. Potential energy to the track: _____________________________________ b. Kinetic energy to the track: ________________________________________ 1 5 3 4 2