# A projectile weighing 20 kg, flying horizontally at a speed of 500 m / s, hits a platform with sand

**A projectile weighing 20 kg, flying horizontally at a speed of 500 m / s, hits a platform with sand weighing 10 tons and gets stuck in the sand. How fast did the platform begin to move?**

To find out the speed acquired by the specified platform, we use the equality: mc * Vc + mpl * Vpl = (mc + mpl) * V, from where we can express: V = (mc * Vc + mp * Vpl) / (mc + mpl).

Data: mс – mass of the projectile (mс = 20 kg); Vс – initial velocity of the projectile (Vс = 500 m / s); mpl is the mass of the platform (mpl = 10 t = 10 ^ 4 kg); Vп – initial platform speed (Vп = 0 m / s).

Let’s calculate: V = (mc * Vc + mpl * Vpl) / (mc + mpl) = (20 * 500 + 10 ^ 4 * 0) / (20 + 10 ^ 4) = 0.998 m / s.

Answer: The specified platform should start moving at a speed of 0.998 m / s.