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To find out how much gravitational potential energy (PE) a 65 kg diver has when standing on a tower 10.0 m above the water, we use the formula PE = m * g * h. Here, "m" is the mass of the diver, "g" is the gravitational force (which is about 9.8 N/kg), and "h" is the height above the water. By putting in the numbers, we find that PE = 65 kg * 9.8 N/kg * 10.0 m, which equals 6370 joules (J).
Now, when the diver jumps and reaches the water at a speed of 14 m/s, we calculate the kinetic energy (KE) using the formula KE = 0.5 * m * v^2. Plugging in the values gives us KE = 0.5 * 65 kg * (14 m/s)^2, which also equals 6370 J. This shows that both the potential and kinetic energies are the same at 6370 J because of the principle of conservation of mechanical energy. This principle means that if there are no outside forces acting on the diver, the total mechanical energy stays the same. The potential energy changes into kinetic energy when the diver jumps.
Next, to find the speed of the diver when he is 5.0 m above the water, we again use energy conservation. At this height, we find the potential energy to be PE' = 65 kg * 9.8 N/kg * 5.0 m, which equals 3190 J. The total energy when the dive starts is still 6370 J. So, the kinetic energy at 5.0 m is KE' = total energy - PE' = 6370 J - 3190 J, which equals 3180 J. Now, to find the speed (v') at this height, we use the formula KE' = 0.5 * m * v'^2. Plugging in the numbers, we get 3180 J = 0.5 * 65 kg * v'^2. Simplifying this, we find v'^2 = (2 * 3180) / 65 which is about 97.54. Finally, taking the square root gives us v' ≈ 9.87 m/s. So, the diver's speed when he is 5.0 m above the water is about 9.87 m/s.