Answer:
We show added energy to a system as +Q or -W
Explanation:
The first law of thermodynamics states that, in an isolated system, energy can neither be created nor be destroyed;
Energy is added to the internal energy of a system as either work energy or heat energy as follows;
ΔU = Q - W
Therefore, when energy is added as heat energy to a system, we show the energy as positive Q (+Q), when energy is added to the system in the form of work, we show the energy as minus W (-W).
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the average kinetic energy of the particles in an object is directly proportional to its TEMPERATURE.
Time taken to reach water :

Now, initial vertical speed , u = 0 m/s.
By equation of motion :

Here, a = g = acceleration due to gravity = 9.8 m/s².
So,

Therefore, the height of the bridge is 3.46 m.
Hence, this is the required solution.