Question

(a) Which combination of energies remains constant when two isolated objects collide elastically? (b) What are the four categories of energy that make up the total energy of a system? Give a brief description of each. (c) You fire a 40 gram rock from ground level using a slingshot. The rock went 3 meters straight up when you released the rock after stretching the rubber band 20 cm. (c1) How much mechanical energy (kinetic plus potential) did the rock have when it reached its peak height? (ignore air resistance.) (c2) If you model the rubber band as an ideal spring, what is its stiffness (spring constant)? (c3) Your body has an energy efficiency of roughly 25%. Using this information. estimate the minimum amount of source energy you have to use in order to hit the target. (c4) How much is your thermal energy increased by this process? A 1 kg ball [ball 1] is launched upward from the ground with a speed of 10 m/s. At a height of 1 meter above the ground, it collides elastically with another 1 kg ball [ball 2] that at that moment was stationary. That ball then starts to travel upwards following the momentum and energy transfer from the first ball. You may not use kinematics to answer the questions below. (x1) What is the first ball's speed just before the collision? (x2) What is the first ball's speed just after the collision? What is the second ball's speed just after the collision? (x3) What is the peak height reached by ball 2?

Answer 1

When the objects collides elastically than mechanical energy remains constant i.e K middot E + P middot E because elastic follow law of conservation of energy. The four energies are. Kinetic energy: Its energy by the body by virtue of its motion. Potential energy: Its energy possessed by the body by virtue of its positions or in configuration of some field. \r\n Mechanical energy: It's the sum of kinetic & potential energy of the body Internal energy: It is the total energy possed by the body by virtue of particular configuration. At its peak it only P middot E NO kinetic energy So E = mgh = 40 times 10^-3 times 9.8 times .3 E = 1.176 J E_total it posses is E = 1.176 J. Now X = 20 cm Now at the beginning E = 1/2 Kx^2 P middot E of sling. 1.176 = 1/2 times K (0.2)^2 1.176 = 1/2 times K times 0.04 K = 1.176