Physics
Bouncing Ball Example
The bouncing ball example illustrates the principles of conservation of energy and momentum. When a ball is dropped, it initially has gravitational potential energy, which is converted to kinetic energy as it falls. Upon hitting the ground, the ball's kinetic energy is transferred to the ground, causing it to bounce back up. This demonstrates the conversion and transfer of energy in a simple yet fundamental way.
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3 Key excerpts on "Bouncing Ball Example"
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler, Heath Jones, Matthew Collins, John Daicopoulos, Boris Blankleider(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
CHAPTER 7 Impulse and momentum 183 FIGURE 7.11 (a) A hard steel ball would rebound to its original height after striking a hard marble surface if the collision were elastic. (b) A partially deflated basketball has little bounce on a soft asphalt surface. (c) A very deflated basketball has no bounce at all. (a) Elastic collision (b) Inelastic collision (c) Completely inelastic collision The next example illustrates a completely inelastic collision in a device called a ‘ballistic pendulum’. This device can be used to measure the speed of a bullet. ANALYSING MULTIPLE‐CONCEPT PROBLEMS EXAMPLE 8 The physics of measuring the speed of a bullet FIGURE 7.12 (a) A bullet approaches a ballistic pendulum. (b) The block and bullet swing upward after the collision. m 1 v 01 (a) m 2 m 1 + m 2 v f (b) h f = 0.650 m A ballistic pendulum can be used to measure the speed of a projectile, such as a bullet. The ballistic pendulum shown in figure 7.12a consists of a stationary 2.50‐kg block of wood suspended by a wire of negligible mass. A 0.0100‐kg bullet is fired into the block, and the block (with the bullet in it) swings to a maximum height of 0.650 m above the initial position (see part b of the drawing). Find the speed with which the bullet is fired, assuming that air resistance is negligible. Reasoning The physics of the ballistic pendulum can be divided into two parts. The first is the completely inelastic collision between the bullet and the block. The total linear momentum of the system (block plus bullet) is conserved during the collision, because the suspension wire supports the system’s weight, which means that the sum of the external forces acting on the system is nearly zero. The second part of the physics is the resulting motion of the block and bullet as they swing upwards after the collision. As the system swings upward, the principle of conservation of mechanical energy applies, since nonconservative forces do no work (see section 6.5).
eBook - PDFWorked Examples in Physics
A Textbook for Private Study
- V. L. Zubov, V. P. Shal'nov(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
Also, he built the first metal dirigible. FIG. 30. 28 Worked Examples in Physics § 7 . WORK, ENERGY, POWER USUALLY , the greatest complications arise in the solution of problems in which the initial energy available in any system suddenly becomes distributed among several bodies (for instan-ce, a body sliding down a triangular prism, as in Examples 106 and 107). Therefore, together with examples serving to clarify the meaning of the concepts of work, energy, and po-wer, some examples involving several interacting bodies are in-cluded in this section. In solving these problems, one should note whether the bodies in an elastic collision are in motion both before and after the interaction. If so, it is necessary to apply the law of conservation of momentum and the law of conservation of energy in calculating the velocities. One must carefully study all the methods of applying these laws simultaneously. The examples in this section employ the concept of perfectly elastic, as well as inelastic, collisions, usually known to the student only from interests outside the classroom. In solving these problems, one should follow with particular care the behaviour of the inter-acting bodies in both cases. A large number of examples involving the calculation of the energy of rotating bodies is given in §8. In working these examples, the student should pay attention to those in which the initial energy of a body is suddenly transformed into two different forms of energy (Example 136). As in the solution of the examples of §6, it is recommended that one should follow all the steps in the ap-plication of the law of conservation of energy. 98. A gun, the barrel of which weighs 450 kg-wt, is fired in a hori-zontal direction. The weight of the projectile is 5 kg-wt and the muzzle velocity is 450 m/sec. When fired, the barrel recoils 45 cm. Find the mean value of the force developed by the anti-recoil device of the gun in absorbing the recoil.
eBook - PDFWhy Toast Lands Jelly-Side Down
Zen and the Art of Physics Demonstrations
- Robert Ehrlich(Author)
- 2020(Publication Date)
- Princeton University Press(Publisher)
93 Conservation of 5 . 7 Coefficient of restitution Momentum and Energy Demonstration The widely familiar executive toy consisting of a row of swinging balls can be used to measure the co-efficient of restitution during collisions. Equipment A Newton's Cradle toy and a transparency made from a piece of graph paper if you want to do the demon-stration on the overhead projector. Discussion As in the previous demonstration, let us consider the problem of a collision between only two balls—with the remaining balls of the toy resting on an impro-vised shelf. But, this time we wish to see how close to being elastic the collisions are, so we do not intro-duce any clay between the balls. In fact, if you added a lump of clay in the previous demonstration, be sure to wipe the balls clean, because even a surface film of clay can seriously reduce the measured elasticity of the collision. Suppose we have an initial state in which both balls are pulled aside, and released from identical 94 „ ,. . angles, so that the lab and center of mass systems Conservation of , ., . . _. . . , , . . . Mnmpnt m nd become identical. You can accomplish this situation E using a rolled-up piece of index card placed between the balls. For this symmetric situation, each ball un-dergoes exactly one-half cycle of a full pendulum swing between impacts, so that the frequency of im-pacts (for small angle swings), is predicted to be / = i/^74 where £ is the length of the strings. A very convenient way you can confirm that the predicted frequency is correct is to activate a metronome at the predicted frequency, and observe that the ball collisions occur at a steady frequency that exactly match that of the metronome. By placing the apparatus on an overhead projector with a ruled transparency beneath it, one can observe how the amplitude of the maximum ball separation decays with time.
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