Question

An 80 kg hunter gets a rope around a 400 kg polar bear. They are stationary and on frictionless level ice, initially 60 m apart. When the hunter pulls the polar bear to him, the polar bear will move?

Answer 1

The two bodies will meet at a point 50 m from the man and 10 m from the bear.

The bear will move, in fact, it will move a total of 10 m towards the direction of the man.

Step-by-step explanation:

Since there is no friction on the ice surface. The law of conservation of Momentum explains that the centre of mass of a system does not move. Meaning that, the bear and the man will meet at the centre of mass of their current setup.

If the position of the man is the origin, that is coordinate x = 0 m

The coordinate of the bear will be x = 60 m

Centre of mass is given as

x = (Σ mx)/(Σ m)

mx for the man = 80 × 0 = 0 kg.m

mx for the bear = 400 × 60 = 24000 kg.m

centre of mass, x = (0 + 24000)/(80 + 400) = 50 m

This means the two bodies will meet at a point 50 m from the man and 10 m from the bear.