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The kinetic energy of a body with a mass m kg and moving at a speed v m/s is given by K.E. = (1/2)*m*v^2 J
The kinetic energy of the ball with a mass 30 kg is 500 J. If the speed of the ball is v, from the equation for kinetic energy given earlier we get:
500 = (1/2)*30*v^2
=> 1000/30 = v^2
=> v = sqrt (100/3)
=> v = 5.774 m/s
The speed of a 30 kg ball with a kinetic energy of 500 J is 5.774 m/s
kinetic energy E=1/2 M.V^2
Where M is mass of body.
and V is velocity of body.
Putting it to above formula-
Hence speed of ball is 5.77m/s.