24.7.....................................
The initial velocity of the ball is v = 23.8 m/s
We know that kinetic energy is given by:
KE = m*v²/2
Where m is the mass in kg, and we know that the energy transfer is 20% of the intial 65J, then we can write:
0.2*65 = (0.046)*v²/2
Solving this equation for v, the velocity, we get:
v = √[0.2*65*2/0.046]
v = 23.8 m/s
Learn more about kinetic energy:
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Answer:
210/6.8 = 1/x
210x = 6.8
x = 0.03238 grams = 32.4 milligrams