Can you solve it? Physics puzzles for smart students

The Department of Physics at Oxford University has suggested today's puzzles.

If you're always burning your mouth on hot coffee, they want to know if that will change your life.

This is the first thing. There is a Cup Pa dilemma.

You are in a hurry. The coffee is too hot for you. Even if you add a fixed amount of cold milk, the coffee will need to cool down before you can drink it.

Coffee cools down more in which case.

• Wait a few minutes before drinking if you want to add milk immediately.

• Just before you drink, add milk.

There are two It's a good idea to fly away.

There is a fly at the bottom of a glass that is sitting on a scale. The fly takes off in a big way. The scale has a readout on it.

• It will go up.

• It falls down.

There are three. The balls are bound.

Two balls are connected by a string. Over the edge of the table is the middle of the string. At the same time, you let go of both balls. The ball 1 flies off the table or the ball 2 hits the side of the table.

There are four. It was fun.

Prove (1/2) x (3/4) x …x (99/100) < 1/10

There is a two line solution.

I'm aware. I have posted these puzzles because of the last one, which is math, not physics.

If you are a smart sixth former at a state school in the UK, you can take part in a free course at Oxford University that will teach you mathematics and physics at a deeper level than the A-level curriculum, preparing you for studying these subjects at university.

If you know someone who loves the hard sciences, please let them know that you don't. You have to register by October 16 to apply.

The Comprehensive Oxford Mathematics and Physics Online School is the brainchild of Alexander Lvovsky, professor of physics at Oxford. The puzzles were suggested by him.

He says that if you can solve the first two puzzles, you should be fine for the course. The final two questions are not easy to answer.

I will return to the UK at 5pm with the answers. There are noSPOILERS.

I put a puzzle here on Mondays. I like to look for puzzles. Email me if you want to suggest one.

The co-author of the children's book series Football School is me. The greatest ever quiz book is available now.

I give talks about math and puzzles to schools. Please let us know if your school is interested.