Answer: 200 J
Step-by-step explanation:
According to the law of conservation of energy, mechanical energy is conserved in a closed system. Therefore, the total mechanical energy of the swing at its highest point should be equal to the total mechanical energy at its lowest point. The total mechanical energy is the sum of the kinetic energy and potential energy of the system.
At the highest point, the swing has only potential energy, which is given as 250 J. At the lowest point, the potential energy is 50 J. Therefore, the kinetic energy at the lowest point can be found by subtracting the potential energy at the lowest point from the total mechanical energy at the highest point:
Total mechanical energy at highest point = Potential energy at highest point
= 250 J
Total mechanical energy at lowest point = Potential energy at lowest point + Kinetic energy at lowest point
Therefore, Kinetic energy at lowest point = Total mechanical energy at lowest point - Potential energy at lowest point
= (Total mechanical energy at highest point) - (Potential energy at lowest point)
= 250 J - 50 J
= 200 J
Therefore, the kinetic energy of the swing at its lowest point is 200 J. The correct answer is 200 J.