Why is gas not used in hydraulic brake system​

Select all the correct answers. which three statements about electromagnetic radiation are true?

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.

Galileos view of arrangement of the universe