Concept:The total mechanical energy gained by the fish is the sum of its newly acquired gravitational potential energy and its kinetic energy.
Formula:$$ \Delta E_{\text{total}} = \Delta P.E + \Delta K.E = mgh + \frac{1}{2}mv^2 $$
Solution:- Mass (\( m \)) = 250 g = 0.25 kg.
- Height (\( h \)) = 1.8 m. Velocity (\( v \)) = 1.1 m/s.
- \( P.E = 0.25 \times 9.8 \times 1.8 = 4.41 \text{ J} \).
- \( K.E = 0.5 \times 0.25 \times (1.1)^2 = 0.125 \times 1.21 = 0.15125 \text{ J} \).
- Total Energy Gained = \( 4.41 + 0.15125 = 4.56125 \text{ J} \).
- Rounding to one decimal place gives 4.6 J. (Using \( g=10 \) yields \( 4.5 + 0.15 = 4.65 \text{ J} \), which also rounds to 4.6 J).
Why other options are incorrect:Option C (4.4 J) represents only the potential energy. Option A (0.15 J) represents only the kinetic energy.
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