The height of a rocket above t seconds after firing is given by s=ut-5t^2, where u represents the initial speed of the rocket. If the initial speed is 70 ms^-1, find the amount of time the rocket is in the air and the time the rocket is above 30m.

What are the applications of electromagnetic waves

Ineed the answer to question 1 , i’m desperate

The magnitude of the magnetic field at a certain distance from a long, straight conductor is represented by b. what is the magnitude of the magnetic field at twice the distance from the conductor? a. at twice the distance, the magnitude of the field is 4b. b. at twice the distance, the magnitude of the field is 2b. c. at twice the distance, the magnitude of the field is b/2.d. at twice the distance, the magnitude of the field is b/4.e. at twice the distance, the magnitude of the field remains equal to b.