Molecular Physics | Thermodynamics Answers

The temperature of 200 g of water decreases from 20 °C to 0 °C in 10 minutes. Calculate

i. the heat lost by the water.

ii. the rate at which the water is losing heat.

iii. the time taken for the water at 0 °C to turn completely into ice.

A conducting and closed container of volume 300 litres contain an ideal gas at a high pressure Pinitial . Now using a pump , the gas it taken out at a constant rate 5 litre per sec . find the time in which the pressure inside the container decreases to Pinitial/100 .

Find the change in entropy when 1.25 kg of steam at 100°C condenses and cools to 50°C.

Problem 8:

A vertically downward force of magnitude 10 N is required to immerse a homogeneous object of weight 40 N completely in water. What is the density of the object?

One- half mole of helium is expanded adiabatically from an initial pressure 5atm and atmosphere of 500K to a final of 1atm. Find the temperature, final volume, the work done by the gas and the change in internal energy of the gas.

A scale reads 328 N when a piece of brass is hanging from it. What does it read (in N) when it is lowered so that the brass is submerged in water?

An oil drum with a diameter of 400mm and height of 2 meters is filled with water. calculate the force of pressure on the bottom of the tank.

. An ideal spring of negligible mass with force constant of 400 N/m is placed on a frictionless horizonal 

table with one end fixed at a wall next to the table. A billiard ball of mass 200 g is pushed against the 

spring, compressing the spring to some distance. After the system is released, the spring returns to 

equilibrium with the billiard ball leaving the table’s edge at 4.00 m/s and hits the floor 80 cm below. 

Using the principle of energy conservation, (a) determine the initial compression of the spring. (b) 

What is the speed of the ball when it hits the floor.

Calculate the mass of a steel plate with a specific heat capacity of 650 J/kg °C, taking into

consideration the steel plate was heated up with a cutting torch while cutting to 925 °C, and was

quenched in 25 It of water with an initial temperature of 22 °C and a specific heat capacity of

3850 J/kg °C. Both the water and the steel plate reached a final temperature of 32 °C. Here we

assume that there was no heat loss. Indicate what info was given, show all formulas and steps.

A basketball floats in a bathtub of water.

The ball has a mass of 0.5 kg and a diameter of 22 cm.

(a) What is the buoyant force?

(b) What is the volume of water displaced by the ball?

(c) What is the average density of the basketball?

You can use

g

= 9

.

8 m/s

2

.