physics 吾識 !!! 急 !!! help!!!

water 's potential energy will be turn in to kinetic energy, then turn to internal energy (raise in temperature)

let gravity = 10 m/s^-2 (since the question didn't provide)

potential energy (PE)= mgh

for each 1kg of water, the PE would be 1 x 10 x 100m
= 1000J

PE => KE => Internal Energy

Assuming no energy loss during the process,

Specific Heat Capacity:
q=mC (delta) T
C stands for specific heat capacity (J/kg ºC)
q is quantity of heat in joules
m = mass
delta T= change is temp

(delta)T = q / mC
= 1000J /4200 kg^(-1)°C^(-1)
= 0.2381°C

Temperature of water = (12 + 0.2381)°C = 12.2381°C

Potential energy of 1 kg water on top of waterfall
= 1g x 100 J = 1000 J
where g is the acceleration due to gravity, taken to be 10 m/s^2

Hence, kinetic energy of water reaching the bottom of the waterfall
= 1000 J

Rise in temperature = 1000/4200 'C = 0.238'C
Temperature of water = (12 + 0.238)'C = 12.24'C