a)positive v - moving forward negative v - moving backwards
b)i)m(v-u)=1.2(-0.8-4)=-5.76
ii)Force=change in momentum/time=5.76/(2.6-1.
=7.2N
c)mAuA+mSuS=mAvA+mBvB
1.2*4+0=1.2*-0.8+3.6vS so (4.8+0.96)/3.6=1.6m/s
loss in KE=1/2mAvA^2 -1/2mBuB^2-1/2mAuA^2=1/2*1.2*4^2-1/2*1.2*0.8^2-1/2*3.6*1.6^2=9.6-0.385-4.608>0 so inelastic