Advertisements
Advertisements
Question
A 50 kg man is running at a speed of 18 km h−1. If all the kinetic energy of the man can be used to increase the temperature of water from 20°C to 30°C, how much water can be heated with this energy?
Advertisements
Solution
Given:-
Mass of the man, m = 50 kg
Speed of the man, v = 18 km/h = `18xx5/18=5"m/s"`
Kinetic energy of the man is given by
`K=1/2mV^2`
`K=(1/2)50xx5^2`
`K=25xx25=625 J`
Specific heat of the water, s = 4200 J/Kg-K
Let the mass of the water heated be M.
The amount of heat required to raise the temperature of water from 20°C to 30°C is given by
Q = msΔT = M × 4200 × (30 − 20)
Q = 42000 M
According to the question,
Q = K
42000 M = 625
`rArrM=625/42xx10^-3`
`=14.88xx10^-3`
=15 kg
APPEARS IN
RELATED QUESTIONS
The amount of water vapour in air is determined in terms of its ______.
Explain the following:
How can you relate the formation of water droplets on the outer surface of a bottle taken out of the refrigerator with the formation of dew?
Calculate the time required to heat 20 kg of water from 10°C to 35°C using an immersion heater rated 1000 W. Assume that 80% of the power input is used to heat the water. Specific heat capacity of water = 42000 J kg−1 K−1.
How do fishes survive in frozen lakes?
Why does a thick glass tumbler crack when very hot water is poured in it?
Study the following diagrams and write down your observations.
Give reasons for the following:
Even when the water in the lakes is frozen, fish can survive.
In a region with a cold climate the aquatic animals can survive at 4 °C, because _______.
Write the name.
The instrument used to study anomalous behaviour of water.
Name the following diagram appropriately.
Write a short note.
Anomalous behaviour of water
Match the columns:
| Column ‘A’ | Column ‘B’ |
| The density of water is maximum at | (a) 0°C |
| (b) 4°C | |
| (c) 100°C |
