Question

Bill and Karen go to the ice-skating rink. Bill has twice the mass of Karen. While they are standing still and talking, suddenly Bill pushes Karen backward. What can you say about the forces between Bill and Karen?

Answer 1

Answer:

forces acting on the two will be equal and opposite in  nature according to Newton's third law of motion.

Explanation:

Given:

mass of Karen, $m$ (let)

then, mass of Bill, $2m$

When they are standing near one another and suddenly Bill pushes Karen then this can be treated as elastic collision and the conservation of momentum applies as:

Sum of final and initial momentum of the system is zero.

$m.v_k-2m.v_b=0$

$2v_b=-v_k$

$v_b=-\frac{v_k}{2}$

But the forces acting on the two will be equal and opposite in  nature according to Newton's third law of motion.