A tuning fork of frequency 254Hz and an open pipe of slightly lower frequency are at 15°C. When sounded together they produce 4 beats per second . On altering the temperature of air the pipe, it is observed that the number of beats per second first diminishes to zero and increases to 4 again. By how much has the temperature of the air in the pipe been altered?

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

c)as speed changes, wavelength and frequency change.

everything changes!

it is a negative acceleration

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.