In a class of 39 students there are 36 girls. The average weight of these girls is 38 Kg and average weight of the full class is 40 kgs. What is the average weight of the boys of the class?
A ball, thrown vertically upward, rises to a height of 80 m and returns to its original position. The magnitude of its displacement after 7 s of motion will be ____. (take g = 10 m/s2)