Can any one suggest how to do these problems. 1) A rocks is dropped from a sea cliff and the sound of it striking the ocean is heard 3.4s later. If the speed of sound is 340m/s, how high is the cliff? 2) An apple is dropped and a multi-flash camera is used to take photographs of the falling apple. If the apple is of 10c in diameter, estimate the time between each photoflash of the apple? I got really stuck with these two problems. Any suggestions how to solve them? Thanks P.