ELASTIC AND INELASTIC COLLISIONS - Weebly

27/01/2017

CONSERVATION QUESTION WARM-UP

1. a) A car (1200kg) moving at 20m/s hits a stationary van (2000kg). If they bounce off each other, and the car moves back at -10m/s, what is the velocity of the van after the collision? b) If instead of bouncing off each other the two vehicles stick together, what will be the velocity of the combined mass?

ELASTIC AND INELASTIC COLLISIONS

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Elastic Collision ? Bodies separate ? Kinetic Energy conserved

ELASTIC AND INELASTIC COLLISIONS

Partially Inelastic Collision ? Bodies separate ? Kinetic Energy NOT conserved

Completely Inelastic ? Bodies stick together ? Kinetic Energy NOT conserved

? Newton's Cradle

ELASTIC COLLISIONS

? Consider: why couldn't the initial movement of one ball result in 2 balls leaving at half the velocity? Would momentum be conserved? Would kinetic energy?

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ELASTIC COLLISIONS

? Elasticity is the property of solid materials to return to their original shape and size after the forces deforming them have been removed

? Elastic collision: no energy lost to deformation, heat or sound

? Billiard balls, ping pong balls, steel balls in Newton's cradle, perfectly bouncy rubber ball

ELASTIC COLLISION EXAMPLE

One pool ball traveling with a velocity of 5 m/s hits another ball of the same mass, which is stationary. The collision is head on and elastic. Find the final velocities of both balls.

V1 = 0m/s V2 = 5m/s

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ELASTIC COLLISION EXAMPLE 2

One pool ball traveling with a velocity of 5 m/s hits another ball of DOUBLE ITS MASS, which is stationary. The collision is head on and elastic. Find the final velocities of both balls.

V1 = -1.6 m/s V2 = 3.3 m/s

PARTIALLY INELASTIC COLLISIONS

? Objects separate (bounce apart) but energy has been lost to deformation, heat and sound

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PARTIALLY INELASTIC COLLISION EXAMPLE

A 3000-kg truck moving with a velocity of 10 m/s hits a 1000kg parked car. The impact causes the 1000-kg car to be set in motion at 12 m/s. Determine: a) The velocity of the truck immediately after the collision b) The loss of kinetic energy c) The degree to which this collision was inelastic (in percent)

a) 6m/s b) 24000J lost c) 84% of initial kinetic energy is remaining

COMPLETELY INELASTIC COLLISIONS

Final velocity of both = 1m/s

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