Answer:
118.4kgm/s
Explanation:
Given parameters:
Weight of object  = 19.6N
     mass of object  = 19.6/9.8  = 2kg
Constant velocity  = 20m/s
Force applied  = 6N
Time taken  = 4s
Unknown:
Final momentum of the object  = ?
Solution:
To solve this problem, we use Newton's second law of motion;
      Ft  = m (v  - u)
F is the force applied
t is the time taken
m is the mass
v is the initial velocity
u is the time taken
      Ft  = mv  - mu
mv is the final momentum;
    So;
   Final momentum  = Ft + mu
 Final momentum  = (19.6 x 4) + (2 x 20) = 118.4kgm/s
