Given the speed and the distance, to find time you can use the formula speed is equal to distance over time. From there you can manipulate the equation for time to equal the distance divided by speed. Time is equal to 18.4 meters divided by 35m/s which equals 0.526 seconds.
By definition, Ampere is a unit of current which is a measure of the amount of charge passing through a point in a circuit per unit of time, with an equivalent charge of 1.602 x 10^(-19) Coulomb per electron. To determine the number of electrons passing through the heater, we use the definition of the current. We calculate as follows:
13.5 A = 13.5 C per second
Charge = 13.5 C/s (10 min) ( 60 s / 1 min)
Charge = 8100 C
Number of electrons = 8100 C / 1.602 x 10^(-19) C per electron
Number of electrons = 5.1 x 10^22 electrons
Therefore, there are 5.1 x10^22 electrons that assed through the heater for 10 minutes.
Answer: the waves travel in an horizontal direction while the strings vibrate in a vertical direction.