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# Kinetic Energy

Energy is the currency of transformation. All systems remain the same unless energy is exchanged between one part and another. Learn here about the energy associated with movement.

# Kinetic energy lost in inelastic collisions

An $$8$$-ton truck traveling at $$20\text{ m/s}$$ hits a parked car of mass $$2000\text{ kg}$$ from behind. If the collision is perfectly inelastic, what is the approximate total loss in kinetic energy?

Assume that the road is frictionless and ignore the deformation of the vehicles.

A wooden block of mass $$4.8\text{ kg}$$ is at rest on a frictionless floor. A bullet of mass $$0.2\text{ kg}$$ is fired at $$500\text{ m/s}$$ towards the block. If the bullet becomes embedded inside the block, how much kinetic energy is lost?

A $$150\text{ kg}$$ bumper car travels at $$12\text{ m/s}$$ due east. It hits an identical bumper car traveling due north at $$16\text{ m/s}.$$ If the cars lock bumpers and stick together, how much kinetic energy is lost in total?

Two balls of masses $$2\text{ kg}$$ and $$3\text{ kg},$$ respectively, move in opposite directions on a frictionless floor. Their respective speeds are $$2\text{ m/s}$$ and $$8\text{ m/s}.$$ If they stick together after a collision, how much kinetic energy is lost in total?

An eagle of mass $$18\text{ kg}$$ is chasing a sparrow of mass $$2\text{ kg}$$ from straight behind with a constant speed of $$13\text{ m/s}.$$ The sparrow flies away at a constant speed of $$7\text{ m/s}.$$ A few seconds later, the sparrow is swallowed by the eagle. If air resistance is negligible, what is the total loss in kinetic energy?

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