Chapter 8, Problem 30A

Can Andrew produce a net impulse on an automobile by sitting inside and pushing on the dashboard? Can the internal forces within a soccer ball produce an impulse on the soccer ball that will change its momentum?

To determine

Whether A can produce an impulse or push an automobile by sitting inside, and whether an impulse could be produced on the soccer ball by internal forces.

Answer to Problem 30A

Just by pushing the dashboard, A cannot produce a net impulse. The internal forces cannot produce an impulse on the soccer ball from inside.

Explanation of Solution

Introduction:

According to Momentum Conservation Principle, if 2 bodies collide in an isolated system, the total momentum of both objects before and after collision will be equal.

Momentum can only be imparted to the automobile, either by igniting the engine or when any external body hits it and imparts its momentum to the automobile. Just by pushing the dashboard, no net impulse would be created as the dashboard is stationary and rigid.

The inner particles like Electron, Proton, etc. that constitute the forces such like Electromagnetic Force or Strong Nuclear Force will not affect the soccer ball unless their atoms/ molecules gains some velocity due to high temperature or collision which can be possible only with the external force impinging on the inner particles of the soccer ball.

If the soccer ball is running with a constant velocity, it will keep on running at the same pace until outer surface friction reduces its velocity and thus momentum. Or, someone kicks it to increase its velocity. If it is at rest then it will stay in the stationary state until any outer body with a similar or massive object hits it with its momentum.

Conclusion:

Just by pushing the dashboard, A cannot produce a net impulse. The internal forces cannot produce an impulse on the soccer ball from inside.