When you heat a certain substance with a difference of temperature

the heat (energy) you must give to it is

where

is the specific heat of that substance (given in J/(g*Celsius))
In this case

Observation: the specific heat of a substance is given in J/(g*Celsius) or J/(g*Kelvin) because on the temperature scale a
difference of 1 degree Celsius = 1 degree Kelvin
Answer:

Explanation:
As we know that system of two boxes are moving on frictionless surface
So here if two boxes are considered as a system
then we have






Now since we know that both the boxes are moving together so force applied by first box on other box is given as



Final velocity = Initial velocity – 9.8 * t
Final velocity = 80.5 – 9.8 * 0.0124 = 80.378 m/s
OR
Final velocity = 80.5 – 9.8 * 16.416 = 80.378 m/s
A. -32 m/s
B. -97 m/s
C. -64 m/s
D. -81 m/s
E. -48 m/s