A 6.8 kg cannon ball leaves a canon with a speed of 188 m/s. Find the average net force applied to the ball if the cannon muzzle is 4.2 m long. 

Asmall electric heater, immersed in 80g of water in a calorimeter of 40j/k raises the temperature from 10.5 degree celsius to 25 degree celsius in 12 minutes. using the same apparatus with 50g of oil instead of water, it is found that the temperature of oil rises from 7 degree celsius to 27 degree celsius in 10 minutes. find specific heat capacity of the oil.