Aknife thrower throws a knife toward a 300-g target that is sliding in her direction at a speed of 2.15 m/s on a horizontal frictionless surface. she throws a 22.5-g knife at the target with a speed of 39.0 m/s. the target is stopped by the impact and the knife passes through the target. determine the speed of the knife after passing through the target.

 = 10.3 m/s

Explanation:

We can solve this exercise using the conservation of the moment; the system is formed by the knife and the target, with an isolated system the moment is conserved during the collision

Knife mass m = 22.5 g and its velocity v₁₀ = 39 m / s, the mass of white is M = 300 gr and its velocity is v₂₀ = -2.15 m / s

Before the crash

     p₀ = m v₁₀ + M v₂₀

After the crash

    = m v₁ₐ + 0

    p₀ =

   m v₁₀ + M v₂₀ = m

     = (m v₁₀ + M v₂₀) / m

Let's calculate

   = (0.0225 39.0 + 0.300 (-2.15)) / 0.0225

   = 10.3 m / s

d) the number of neutrons plus the number of protons

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