Which of the following objects has the largest momentum? (A) A bullet fired from a rifle (B) A football quarterback running at top speed (C) A horse walking at about 2 mileslhour (D) An elephant standing still

							The correct option is (C).
Momentum (p) of an object is equal to the mass of the object (m) time’s speed of the object (v).
So, p = mv …… (1)
a) Let us consider the average mass of a bullet is 0.2 kg (m = 0.2 kg) and the average speed of bullet is 400 m/s (v = 400 m/s).
Using equation (1), the momentum of the bullet will be,
p = mv
 = (0.2 kg) (400 m/s)
  = 80 kg. m/s …… (2)
 From equation (2) we observed that, the average momentum of the bullet will be 80 kg. m/s.
b) Let us consider the average mass of a football is 0.5 kg (m = 0.5 kg) and the top speed of football is 30 m/s (v = 30 m/s).
Using equation (1), the momentum of the football will be,
p = mv
 = (0.5 kg) (30 m/s)
 = 15 kg. m/s …… (3)
 From equation (3) we observed that, the momentum of the football will be 11 kg. m/s.
c) Let us consider the average mass of a horse is 500 kg (m = 500 kg). The given speed of horse is 0.9 m/s (v = 2 miles/hour).
Using equation (1), the momentum of the horse will be,
p = mv
 = (500 kg) (0.9 m/s)
 = 450 kg. m/s …… (4)
 From equation (4) we observed that, the average momentum of the horse will be 450 kg. m/s.
d) Since the elephant is still standing, therefore, the speed of the elephant would be zero (v=0). Using equation (1), the momentum of the elephant would be zero.
From the above observation we conclude that, a horse walking at about 2 miles/hour has the largest momentum. Thus option (C) is correct.