3. The centre of gravity of a trapezium with parallel sides a and b lies at a distance of y from the base b, as shown in the below figure. The value of y is
7. If a number of forces acting at a point be represented in magnitude and direction by the three sides of a triangle, taken in order, then the forces are not in equilibrium.
8. The rate of change of momentum is directly proportional to the impressed force, and takes place in the same direction in which the force acts. This statement is known as
