A one tonne crane increases its speed from 30km/h to 108km/h in 35 seconds. Calculate the change in momentum

21.67kgms-1

Explanation:

30kmh-1 = ( 30× 1000) ÷ 3600 = 8.33 ms-1

108 Kmh-1 = (108 × 1000) ÷ 3600 = 30ms-1

change in momentum = ∆mv

= 1000000 kg ( 30 -8.33) ms-1

= 21.67 ×10^6 kgms-1

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 .