a 2 kg object is released from rest from a height of 10 m above the ground.calculate the kinetic energy at the moment it reaches 4 m above the ground with potential energy 200J

To calculate the kinetic energy of an object, we need to know its mass and velocity. However, in this case, we have the potential energy of the object when it is 4 m above the ground along with its mass.

Let's break down the problem step by step:

Step 1: Calculate the potential energy of the object at a height of 4 m.
Given that the potential energy is 200 J, we can use the formula for potential energy, which is calculated as mass (m) multiplied by the acceleration due to gravity (g) multiplied by the height (h):
Potential energy (PE) = m * g * h

Since the mass of the object is given as 2 kg and the height is 4 m, and the acceleration due to gravity is approximately 9.8 m/s², we can substitute these values into the formula:
PE = 2 kg * 9.8 m/s² * 4 m

Simplifying the equation:
PE = 78.4 J

So, the potential energy of the object when it is 4 m above the ground is 78.4 J.

Step 2: Calculate the kinetic energy of the object.
The total mechanical energy of an object is the sum of its potential energy (PE) and kinetic energy (KE). Therefore, we can find the kinetic energy by subtracting the potential energy from the total mechanical energy.

Given that the object was released from rest, it only has potential energy at the moment it reaches 4 m above the ground. This means that the total mechanical energy consists only of the potential energy at that point.

So, the kinetic energy can be calculated as:
KE = Total Mechanical Energy - Potential Energy

Since the total mechanical energy is equal to the potential energy in this case, we can substitute the values:
KE = PE - PE
KE = 78.4 J - 78.4 J
KE = 0 J

Therefore, the kinetic energy of the object at the moment it reaches 4 m above the ground is 0 J.