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Question

A wad of gum is shot at a block of wood. In which case does the gum exert the larger impulse on the block, when it sticks or when it rebounds?

Answer 1

What a good question! Here's my guess:
When a piece of gum rebounds, it still retains some energy. When it sticks, all the energy is absorbed by the wood. So the gum that sticks transfers more energy to the wood.

Answer 2

i believe it would be the same in either case, as the formula for impulse is impulse = mass x change in velocity

an example of the impulse being the same is when you drop 2 identical eggs from the same height, one into soft foam, one onto tile, the impulse on the eggs is identical. if you need a further explanation email me @ [e-mail]

Answer 3

♠ the total momentum of wad-wood system M=m1*v1 is conserved in either case; here m1 is mass of wad, v1 is its speed;
♣ if they stick then M=m1*u +m2*u, where m2 is mass of wood, u is their common speed;
♦ if they rebound then M=-m1*u1+m2*u2; minus showing opposite direction;
♥ thus m1*u +m2*u = -m1*u1+m2*u2, hence m2*(u2-u) = m1*(u1+u) >0, hence u2>u; conclusion: momentum of wood is larger when they rebound.