What is most nearly the elongation of an aluminum bar (3 cm x 3 cm) when loaded in tension to its yield point

An object moves from the position +34m to the position -15m in 15 seconds. what is it's total displacement? what is it's average velocity?

Determine the fraction of the magnitude of kinetic energy lost by a neutron (m1 = 1.01 u) when it collides head-on and elastically with a target particle at rest which is 21h (heavy hydrogen, m = 2.01 u).

Convection currents are caused by differences in what two things?