how does the impulse momentum theorem and conservation of momentum show the existence of the third law of motion? impulse momentum theorem- the force of an object a that hits object b will create a force. The force that object b exerts back on object a should be the same as the force object a exerts on object b. So the impulse should be equal in magnitude. conservation of momentum-since the sum of the initial velocities of both objects are equal to the sum of the final velocities. Therefore, there is the same amount of force exerted back on each objects. did I explain this right?