Can someone explain how the weight of the block is 10.26N, with reference to an appropriate law of motion?

If the speed of a particle triples ,by what factor does its kinetic energy increase?

What is the rate of change in a objects position?

Asolid round steel rod 6.25 mm in diameter and 375 mm long is rigidly bonded to the end of solid square brass rod 25 mm on a side and 300 mm long. the geometric axes of the bare are along the same line. an axial tensile force of 5.4 kn is applied at the extreme ends of the assembly. for steel e = 200 gpa and for brass e = 90 gpa. determine the total elongation for the assembly.