Answer:
1) 2197.44 J
2) 0 J
3) 2197.44 J = Constant
4) 2197.44 J
5) Approximately 8.86 m/s
Explanation:
The given parameters are;
The mass of the diver, m = 56 kg
The height of the cliff, h = 4.0 m
The speed with which the diver is moving, vₓ = 8.0 m/s
The gravitational potential energy = Mass, m × Height of the cliff, h × Acceleration due to gravity, g
1) Her gravitational potential energy = 56 × 4.0 × 9.81 = 2197.44 J
2) The kinetic energy = 1/2·m·u²
Where;
u = Her initial velocity = 0 when she just leaves the cliff
Therefore;
Her kinetic energy when she just leaves the cliff = 1/2 × 56 × 0² = 0 J
3) The total mechanical energy = Kinetic energy + Potential energy
The total mechanical energy is constant
Her total mechanical energy relative to the water surface when she leaves the cliff = Her gravitational potential energy = 2197.44 J = Constant
4) Her total mechanical energy relative to the water surface just before she enters the water = 2197.44 J
5) The speed with which she enters the water, v, is given from, v² = u² + 2·g·h
Where;
u = The initial velocity at the top of the cliff before she jumps= 0 m/s
∴ v² = 0² + 2 × 9.81 × 4 = 78.48
v = √78.48 ≈ 8.86 m/s
The speed with which she enters the water, v ≈ 8.86 m/s
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