Applying conservation of energy, the initial total kinetic energy is equal to the total final energy.
`E_i = E_f`
Since the rock starts at ground level, its height zero (h=0). So, its potential energy is zero. Thus, the initial total energy consist only of the given kinetic energy.
`E_i = KE_i +PE_i`
`E_i= 741 +0`
`E_i =741`
Then, the rock rises until it ceases moving. At this height h, the velocity of the rock is zero (v=0). So, its kinetic energy is zero. Thus, the final total energy consist only of the potential energy.
`E_f =KE_f + PE_f`
`E_f= 0 + PE_f`
`E_f=PE_f`
Setting the initial total energy and final total energy equal to each other, then the potential energy at height h is:
`E_i=E_f`
`741 =PE_f`
Therefore, when the rock reaches the point it stops moving, its gravitational potential energy is 741 Joules.
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