What is the magnitude of the force exerted on the bottom of the bottle?

If you place a magnet under a clear dish, and sprinkle iron fillings over it, above what part of the magnet will most of the fillings gather

What quantity do units represent in value

The stopwatch used by a student to measure velocity of a pulse in a slinky was of least count 0.1 second. he stops the stopwatch when a pulse has made 3 journeys from one end to the other of the slinky. he finds the seconds hand to be at 52nd division. calculate the correct time noted by him.