Party Shakers-2

Four couples attended a party. One couple was you and your spouse; another was Rama and Sita. Some people shook hands with one another, but nobody shook hands with oneself or with one's own spouse.

After the party, you asked each person (except yourself) how many different people the person had shaken hands with. Each person replied with a different number--and each person's reply was truthful.

You shook hands with Sita. Did your spouse shake hands with Sita? With Rama?

Humble Bicycle and friction

All of us have rode the bicylce at some point of time...and we all know that friction always opposes the motion.
So, what is the direction of frictional forces on the front and rear wheel?
a) When pedalling
b) When idling (not pedalling).

Source: This was a question from Resonance (an IISc publication for undegrads and grads) may be in he year 1998/97.

Hey Water, Can I drink you?

The way we pollute water, me thinks thatone day we will all have to go to Mars to get some drinking water... So, NASA decides to send a spaceship to Mars to explore this possibility... The spaceship breaks the law of relativity using a loophole and reaches Mars within an Earth day. They reach Mars... find the frozen water in the lakes, take it to a region of 5 degrees C in Mars, melt it and then filter it. finally, to check safety of drinking it, he finds the pH which is close to 8. He goes on to check the chemical components of water thinking that there must be something basic in the water but finds it to be pure water. Explain the paradox.

Of sand mixtures and thermodynamics!

Hope you all are familiar with the common experience with haldiram bhujia...The big chunks of the yummy stuff is always on the top and separates out from the rest of the smaller sized bhujia. I say this because, we always had a fight at home as to who gets to open the pack! Similarly...if you shake a mixture of sand, you will find the bigger sized stones always on top.

Now the question is: Since shaking is a random process, we should expect the particles to be randomly distributed (to have more disorder, increase in entropy) but we have an apparent order (separation of particles into different sizes). Isn't it a against our second law of thermodynamics? Where is the catch? :)
@

Party shakers...

In any party, there is a lot of handshaking. Show that there are atleast two people who have shaken hands with an equal number of people.

(credits:tuku)

The clank of the little kids...

You walk into a school with 100 kids all of which are hyperactive. The school has 100 lockers one for each numbered from 1 to 100. The first kid walks into the locker room and opens all of them. The second kid zooms past and changes the status of every even numbered locker. The third kid waltzes through the room changing the status of lockers divisible by 3 (3,6,9 etc.), the fourth one does the same with all that is divisible by 4 and they do the closing and opening alternately. Which lockers are open at the end of the day? And what's your logic?