A plane has a speed of 285 km/h west relative to the air. A wind blows 25 km/h east relative to the ground. what are the planes speed and direction relative to the ground?

260 km/h

Explanation:

Motion is said to be relative when the motion observed by the observer depends on the location (frame) of the observer.

When two objects are moving in opposite directions, the relative motion is obtained by subtraction.

Hence  the plane is moving at (285 - 25) km/h giving 260 km/h

insects!

explanation:

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.