PHY183-Lecture19pre - 1 Physics for...

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Unformatted text preview: 1 February 16, 2012 Physics for Scientists&Engineers 1 1 Physics for Scientists & Engineers 1 Physics for Scientists & Engineers 1 Spring Semester 2012 Lecture 19 Totally Inelastic Collisions, Ballistic Pendulum Head-on Collision Head-on Collision Consider a head-on collision of a full-size SUV, with mass M = 3023 kg, and a compact car, with mass m = 1184 kg Each vehicle has an initial speed of 22.35 m/s and are moving in opposite directions The two cars crash into each other and become entangled • Totally inelastic collision What are changes in the two cars velocities? February 16, 2012 Physics for Scientists&Engineers 1 2 Head-on Collision Head-on Collision SOLUTION • Calculate the final velocity that the combined mass has immediately at the collision • The velocity change for the SUV is • The velocity change for the compact car is February 16, 2012 Physics for Scientists&Engineers 1 3 v f, x = mv x − Mv x m + M = m − M m + M v x = 1184 kg − 3023 kg 1184 kg + 3023 kg (22.35 m/s) = − 9.77 m/s Δ v SUV = − 9.77 m/s − ( − 22.35 m/s) = 12.58 m/s Δ v compact = − 9.77 m/s − (22.35 m/s) = − 32.12 m/s Head-on Collision Head-on Collision We obtain the corresponding average acceleration by dividing the velocity changes by the time interval ∆ t The magnitude of the acceleration experienced by the driver of the compact car is bigger than the acceleration experienced by the drive of the SUV Newton’s Third Law tells us that the two vehicles exert the same force on each other It is safer to be in the SUV than in the compact car because the resulting acceleration is less February 16, 2012 Physics for Scientists&Engineers 1 4 a compact = Δ v compact Δ t a SUV = Δ v SUV Δ t a compact a SUV = Δ v compact Δ v SUV = 32.12 m/s 12.58 m/s = 2.55 February 16, 2012 Physics for Scientists&Engineers 1 5 Experiment: Totally Inelastic Collision Experiment: Totally Inelastic Collision Ballistic Pendulum Ballistic Pendulum A ballistic pendulum can be used to measure muzzle speeds of projectiles shot from firearms It consists of a block of material into which the bullet is fired The block is suspended so that it forms a pendulum February 16, 2012 Physics for Scientists&Engineers 1 6 2...
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This note was uploaded on 04/02/2012 for the course PHY 183 taught by Professor Wolf during the Spring '08 term at Michigan State University.

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PHY183-Lecture19pre - 1 Physics for...

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