If you travel 30 miles somewhere and then come home again your distance is 60 miles. Your displacement is 0 because it is the ending position minus the beginning position, which are the same place (home). In other words, displacement is a vector and distance is a scalar.
You can use the impulse momentum theorem and just subtract the two momenta.
P1 - P2 = (16-1.2)(11.5e4)=1702000Ns
If you first worked out the force and integrated it over time the result is the same
Efficiency = (useful output) / (input)
Efficiency = (35 J) / (125 J) = 0.28 = 28%
Answer:
Temperature, T = 3.62 kelvin
Explanation:
It is given that,
Total number of gas molecules, 
Her body is converting chemical energy into thermal energy at a rate of 125 W, P = 125 W
Time taken, t = 6 min = 360 s
Energy of a gas molecules is given by :

, k is Boltzmann constant


T = 3.62 K
So, the temperature increases by 3.62 kelvin. Hence, this is the required solution.