Question

two gliders with different masses move toward each other on a frictionless air track. after they collide, glider b has a final velocity of 2m/s. the gliders are equip so that they stick together when they collide. find the common final x-velocity and compare the initial and final kinetic energies of the system.

Answer 1

Because the gliders stick together, their speed is the same after the collision

$v=2\ (m/s)$ .

The initial kinetic energy of the system

$KE_i=m_1v_1^2/2+m_2v_2^2/2$

The final kinetic energy of the system

$KE_f=(m_1+m_2)v^2/2$

Since the impact is completely inelastic, part of the energy is expended and no longer passes back into the kinetic energy of motion of these bodies. So,

$KE_i>KE_f$ .