11.

Magnesium powder, placed in an air-conditioned glass container at 1.0 bar, is burnt by focusing sunlight. Part of the magnesium burns off, and some is left behind. The pressure of the air in the container after it has returned to room temperature is approximately.

• 1.0 bar   

• 0.2 bar  

• 1.2 bar

• 0.8 bar

When a magnet is made of fall free in air, it falls with an acceleration of 9.8 m s^-2. But when it is made to fall through a long aluminum cylinder, its acceleration decreases, because

• A part of the gravitational potential energy is lost in heating the magnet.

• A part of the gravitational potential energy is los in heating the cylinder.  

• The said experiment was done in the magnetic northern hemisphere.   

• The cylinder shields the gravitational force.  

A solid cube of side L floats on water with 20% of its volume under water. Cubes identical to it are piled one by one on it. Assume that the cubes do not slip or topple, and the contact between their surfaces is perfect. How many cubes are required to submerge one cube completely?

• 4

• 5

• 6

• Infinite

An overweight person runs 4 km everyday as an exercise. After losing 20% of his body weight, if he has to run the same distance in the same time, the energy expenditure would be

• 20% more    

• The same asearlier

• 20% less

• 40% less     

On exposure to desiccation which of the following bacteria are least likely to experience rapid water loss?

• Isolated rods  

• Rods in chain

• Cocci in chain

• Cocci in clusters

A cupboard is filled with a large number of balls of 6 different colors. You already have one ball of each color. If you are blind-folded, how many balls do you need to draw to be sure of having 3 color-matched pairs of balls?

• 3

• 4

• 5

• 6

The conductance of a potassium chloride solution is measure using the arrangement depicted below. The specific conductivity of the solution in Sm^-1, when there is no deflection in the galvanometer, is

• 1.0 

• 0.5 

• 2.0

• 1.5

What is the half-life of the radio isotope whose activity profile is shown below?

• 1 day

• 3 days

• 2 days

• 4 days

A bell is rung before giving food to a dog. After doing this continuously for 10 days, which of the following is most likely to happen?

• The dog learns to ignore the bell.   

• The dog salivates on hearing the bell.  

• The dog ignores food and runs towards the bell.

• The dog will not eat food without hearing the bell.   

For an elastic material, strain is proportional to stress. A constant stress is applied at time t₁. Which of the following plots characterizes the strain in that material?