Physics, Chemistry, Mathematics Forums

The word document in 1997-2003 format is attached below.
The question is typed there

Consider a cubical vessel of edge length a having a small hole in one of it's walls.The total thermal resistance of the walls is r.At time t=0,it contains air at atmospheric pressure pa and temperature To.The temperature of the surrounding air is Ta(Ta>To).Find the amount of the gas (in moles) in the vessel at time t.Take CV OF AIR TO BE 5R/2. 

One mole of FeO slowly converted to Fe3O4 completely. How many mole of this compound will be formed?

A block exerts a force of 9.8 N on a table. that table exerts a force of 10 N on the block .Assume g=9.8 m/s^2
then
a)the block exerts a force of 10 N on the table
b)the block exerts a force of 19.8 N on the table
c)the block exerts a force of 9.8 N on the table
d) the block has an upward acceleration

please explain the answer

chemistry

Q.1]For each k to be an element of N ,let c_k denote the circle whose equation is x²+y²=k².On the circle c_k,a particle moves k units int he anticlockwise direction.After completing its motion on c_k,the particle moves to c_k+1 int he radial direction.The motion of the particle continues in this manner.The particle starts at (1,0).If the particle crosses the positive direction of the x-axis for yhe first time on the circle c_n then n is :[a] 7 [b] 6 [c] 2 [d] none of these.

Q.2] Two distinct chords drawn from the point (p,q) on the circle x²+y²=px +qy,where pq is not equal to 0,are bisected by the x axis.Then [a] mod p=modq [b] p²=8q² [c] p²<8q² [d]p²>8q².Please reply.

Fine particles of a substance are to be stored in a heap on a horizontally circular plate of radius a . If the co-efficient of static friction between the particles is k, the maximum possible height of cone is :
a) ak
b) ak/2
c) a/k
d) ak²

In a Quincke's experiment ,the sound intensity has a minimum value I at a particular position.As the sliding tube is pulled out by a distance of 16.5 mm ,the intensioty increases to a maximum of 9I.Take the speed of sound,in air to be 330m/s.(a) Find the frequency of the sound source.

Somebody please try to solve H.C.Verma's question no.48 and also explain the solution.Question has an image therefore cannot post it here.

A ship loaded with passengers wants to cross the river 200m wide flowing with a speed of 4 m/s. Boat moves towards north east with a speed of 4 m/s. when the boat had traveled half the dstance ,then passenger asked to sailor that the have to go to just opposite shore from where they have started. the find the direction to which the boat hasto travel to reach the opposite point from where they have started. a hint diagram is given.

ans:-2tan¯¹(1/2)