$A$ man weighing $70 \,kg$ carries a weight of $10 \,kg$ to the top of a tower $100 \,m$ high. Calculate the work done.

(N/A) The work done by the man is equal to the change in the potential energy of the system (man + weight).
The total mass $m$ is the sum of the man's mass and the weight he carries:
$m = 70 \,kg + 10 \,kg = 80 \,kg$
The height $h$ is $100 \,m$.
Taking the acceleration due to gravity $g = 9.8 \,m/s^2$,the work done $W$ is calculated as:
$W = m \times g \times h$
$W = 80 \,kg \times 9.8 \,m/s^2 \times 100 \,m$
$W = 78400 \,J$ (or $7.84 \times 10^4 \,J$).