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Question
A molecule in a gas container hits a horizontal wall with speed 200 m s–1 and angle 30° with the normal, and rebounds with the same speed. Is momentum conserved in the collision? Is the collision elastic or inelastic?
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Solution
Speed of molecule u = 200 m s-1, θ = 30°
Speed after rebound ν = 200 m s-1
∵ Momentum is conserved in every type of collision.
Therefore, momentum will be conserved in this collision also.
kinetic energy of the system when hitting the wall `"K"_1 = 1/2 "m""u"^2`
= `1/2"m" (200)^2 "J"`
kinetic energy after collision `"K"_2 = 1/2 "m""ν"^2`
= `1/2"m" (200)^2 "J"`
∴ The collision is elastic collision.
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