Water waves in a small tank are 7.5-cm long. They pass a given point at a rate of 2.5 waves per 20 seconds.
A) What is the speed of the water waves?
I
B) What is the period (T) of the waves?

The change in temperature is 9.52°C

Explanation:

Since, the heat supplied by the electric kettle is totally used to increase the temperature of the water.

Thus, from the law of conservation of energy can be stated as:

Heat Supplied by Electric Kettle = Heat Absorbed by Water

Heat Supplied by Electric Kettle = m C ΔT

where,

Heat Supplied by Electric Kettle = 20,000 J

Mass of water = m = 0.5 kg

Specific Heat Capacity of Water = C = 4200 J/kg.°C

Change in Temperature of Water = ΔT

Therefore,

20,000 J = (0.5 kg)(4200 J/kg.°C) ΔT

ΔT = 20,000 J/(2100 J/°C)

ΔT = 9.52°C