Explanation:
Given that,
The mass of rock, m = 2.35-kg
It was released from rest at a height of 21.4 m.
(a) The kinetic energy is given by : 
As the rock was at rest initially, it means, its kinetic energy is equal to 0.
(b) The gravitational potential energy is given by : 
It can be calculated as :

(c) The mechanical energy is equal to the sum of kinetic and potential energy such that,
M = 0 J + 492.84 J
M = 492.84 J
Hence, this is the required solution.
The magnitude of the average impulsive force imparted to the ball if it is in contact with the bat is 6000 N
The mass of the baseball, m = 0.15 kg
The speed at which it moves, v = 30 m/s
Time at which the baseball was in contact with the bat, t = 0.75 ms
t = 0.75/1000 s
t = 0.00075 s
The impulsive force is given by the formula:

Substitute m = 0.15 kg, v = 30, and t = 0.00075s into the formula above:

The magnitude of the average impulsive force imparted to the ball if it is in contact with the bat is 6000 N
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Answer:
500J
Explanation:
The arrow will have an energy of 500J after it has been released from its state of rest.
This is compliance with the law of conservation of energy which states that "in every system, energy is neither created nor destroyed but transformed from one form to another".
- The energy at rest which is the potential energy is 500J
- This energy will be converted to kinetic energy in total after the arrow has been released.
- This way, no energy is lost and we can account for the energy transformations occurring.