We need to apply the conservation of momentum formula
[tex]m1u1+m2u2=m1v1+m2v2[/tex]Where m1 and m2 are the masses, u1 and u2 are the initial velocities of each mass, and v1 and v2 are the final velocities of each mass
we have
m1= 2.5 kg
u1= 4.2 m/s
m2=2.5 kg
u2= 0 m/s
v1=0 m/s
v2=?
we substitute
[tex]2.5(4.2)+2.5(0)=2.5(0_{})+2.5(v_2)[/tex]therefore
[tex]v2=4.2\text{ m/s}[/tex]ANSWER
v2=4.2 m/s
