What is the frequency heard by a person driving at 15 m/s toward a factory whistle emitting a
frequency of 800. Hz? (speed of sound that day 340. m/s)

835.29 Hz

Explanation:

When moving towards the source of sound, frequency will be given by

f*=f(vd+v)/v

Where f is the freqiency of the source, vd is the driving speed, v is the speed of sound in air, f* is the inkown frequency when moving forward.

Substituting 800 Hz for f, 340 m/s for v and 15 m/s for vd then

f*=800(15+340)/340=835.29411764704 Hz

Rounded off, the frequency is approximately 835.29 Hz

conservation of mass

mass before something happens = mass afterwards

electric field is a function of 1/r^2

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