Find the kinetic energy of a ball of mass 200 grams moving at a speed of 20m/s

We have a mass of 200g (0.2kg) moving at 20m/s

Kinetic Energy KE = ½ mv^2 where m is mass and v is velocity

Actually, v is a vector quantity, so KE = ½ mv•v

The dot product of 2 vectors a and b is abCosθ where θ is the angle between the vectors.

Obviously v•v = v^2 Cos0 = v^2

In this case, we have KE = ½ (0.2)(20^2) = 40kg-m^2/s^2 = 40J

So we have kinetic energy in the amount of 40 Joules.

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