Given, mass of ball m=0.5‌kg Initial velocity, u=10ms−1 Change in momentum, ∆p=8‌kg⋅ms−1 According to given situation change in momentum of ball ‌∆p‌=pf−pi ⇒8‌=mv−m(−u) ⇒8‌=m(v+u) ⇒‌8=0.5(v+10) ⇒16‌=v+10 ⇒‌v‌=6ms−1