Physics-
General
Easy
Question
The only possibility of heat flow in a thermos flask is through its cork which is 75 cm2 in area and 5 cm thick. Its thermal conductivity is 0.0075 cal/cmsecoC. The outside temperature is 40oC and latent heat of ice is 80 cal g–1. Time taken by 500 g of ice at 0oC in the flask to melt into water at 0oC is
- 2.47 hr
- 4.27 hr
- 7.42 hr
- 4.72 hr
The correct answer is: 2.47 hr
Þ 
Þ t = 8.9 ´ 103 sec = 2.47 hr.
Related Questions to study
Physics-
A composite metal bar of uniform section is made up of length 25 cm of copper, 10 cm of nickel and 15 cm of aluminium. Each part being in perfect thermal contact with the adjoining part. The copper end of the composite rod is maintained at 
and the aluminium end at 
. The whole rod is covered with belt so that there is no heat loss occurs at the sides. If 
and 
, then what will be the temperatures of 
and 
junctions respectively
A composite metal bar of uniform section is made up of length 25 cm of copper, 10 cm of nickel and 15 cm of aluminium. Each part being in perfect thermal contact with the adjoining part. The copper end of the composite rod is maintained at and the aluminium end at . The whole rod is covered with belt so that there is no heat loss occurs at the sides. If and , then what will be the temperatures of and junctions respectively
Physics-General
Physics-
Three rods made of the same material and having the same cross section have been joined as shown in the figure. Each rod is of the same length. The left and right ends are kept at and 
respectively. The temperature of the junction of the three rods will be
Three rods made of the same material and having the same cross section have been joined as shown in the figure. Each rod is of the same length. The left and right ends are kept at and respectively. The temperature of the junction of the three rods will be
Physics-General
Physics-
A wall is made up of two layers A and B. The thickness of the two layers is the same, but materials are different. The thermal conductivity of A is double than that of B. In thermal equilibrium the temperature difference between the two ends is 
. Then the difference of temperature at the two surfaces of A will be
A wall is made up of two layers A and B. The thickness of the two layers is the same, but materials are different. The thermal conductivity of A is double than that of B. In thermal equilibrium the temperature difference between the two ends is . Then the difference of temperature at the two surfaces of A will be
Physics-General
Physics-
Newton’s law of cooling, holds good only if the temperature difference between the body and the surroundings is
Newton’s law of cooling, holds good only if the temperature difference between the body and the surroundings is
Physics-General
Physics-
The temperature of a liquid drops from 
to 361 K in 2 minutes. Find the time during which temperature of the liquid drops from 
to 
. Temperature of room is 
The temperature of a liquid drops from to 361 K in 2 minutes. Find the time during which temperature of the liquid drops from to . Temperature of room is
Physics-General
Physics-
The ratio of radiant energies radiated per unit surface area by two bodies is 16 : 1, the temperature of hotter body is 1000K, then the temperature of colder body will be
The ratio of radiant energies radiated per unit surface area by two bodies is 16 : 1, the temperature of hotter body is 1000K, then the temperature of colder body will be
Physics-General
Physics-
Two identical objects A and B are at temperatures TA and TB respectively. Both objects are placed in a room with perfectly absorbing walls maintained at temperatures T 
The objects A and B attain temperature T eventually which one of the following is correct statement
Two identical objects A and B are at temperatures TA and TB respectively. Both objects are placed in a room with perfectly absorbing walls maintained at temperatures T The objects A and B attain temperature T eventually which one of the following is correct statement
Physics-General
Physics-
An open knife edge of mass 'm' is dropped from a height 'h' on a wooden floor. If the blade penetrates upto the depth 'd' into the wood, the average resistance offered by the wood to the knife edge is
An open knife edge of mass 'm' is dropped from a height 'h' on a wooden floor. If the blade penetrates upto the depth 'd' into the wood, the average resistance offered by the wood to the knife edge is
Physics-General
Physics-
If 
and 
represent the work done in moving a particle from A to B along three different paths 1, 2 and 3 respectively (as shown) in the gravitational field of a point mass m, find the correct relation between and
If and represent the work done in moving a particle from A to B along three different paths 1, 2 and 3 respectively (as shown) in the gravitational field of a point mass m, find the correct relation between and
Physics-General
Physics-
A ball hits the floor and rebounds after inelastic collision. In this case
A ball hits the floor and rebounds after inelastic collision. In this case
Physics-General
Physics-
A ball is attached to a horizontal cord of length L whose other end is fixed a peg is located at a distance h (= 4L/5) directly below the point of attachment of the cord. What will be the speed of the ball when it reaches the top of its circular path about the peg?
A ball is attached to a horizontal cord of length L whose other end is fixed a peg is located at a distance h (= 4L/5) directly below the point of attachment of the cord. What will be the speed of the ball when it reaches the top of its circular path about the peg?
Physics-General
Physics-
An engine approaches a hill with a constant speed. When it is at a distance of 0.9 km it blows a whistle, whose echo is heard by the driver after 5 sec. If speed of sound in air is 330 m/s, the speed of engine is
An engine approaches a hill with a constant speed. When it is at a distance of 0.9 km it blows a whistle, whose echo is heard by the driver after 5 sec. If speed of sound in air is 330 m/s, the speed of engine is
Physics-General
Physics-
The number of beats produced per second by two vibrations: x1 =x0 sin 646pt and x2 = x0 sin 652 pt is
The number of beats produced per second by two vibrations: x1 =x0 sin 646pt and x2 = x0 sin 652 pt is
Physics-General
Physics-
An Indian submarine and an enemy submarine move towards each other during maneuvers in motionless water in the Indian ocean. The Indian submarine moves at 50 km/h, and the enemy submarine at 70 km/h. The Indian sub sends out a sonar signal (sound wave in water) at 1000 Hz. Sonar waves travel at 5500 km/h. What is the frequency detected by the Indian submarine
An Indian submarine and an enemy submarine move towards each other during maneuvers in motionless water in the Indian ocean. The Indian submarine moves at 50 km/h, and the enemy submarine at 70 km/h. The Indian sub sends out a sonar signal (sound wave in water) at 1000 Hz. Sonar waves travel at 5500 km/h. What is the frequency detected by the Indian submarine
Physics-General
Physics-
if speed is plotted against x-axis and kinetic energy against y –axis, then the graph obtained has a shape similar to that of
if speed is plotted against x-axis and kinetic energy against y –axis, then the graph obtained has a shape similar to that of
Physics-General
