Fill in the blanks: Newton’s first law is often called the law of _____; Newton’s second law is the law of _____; and Newton’s third law is the law of _____ and _____.
ANSWER: STEP 1:- As we know the 1st law of Newton is the law of inertia which states that, If there is no external force, then the object in motion will continue it’s motion without change in velocity and the object in rest will remain at rest. But this is what conservation of linear momentum is, which tells that the momentum of the object will be unchanged if there is no external force. As momentum does not change, so the velocity will also not change and remain constant. STEP 2:- For the 2nd law, force is mass times acceleration. When the force is zero the acceleration has to be zero, because mass cannot be zero. Mass is an invariant quantity. So, this law also tells about the conservation of momentum. Because the acceleration is zero means no change in velocity. If the velocity does not change, it implies the conservation of linear momentum. STEP 3:- Coming to the 3rd law which says that, “every action has an equal and opposite reaction”, this law also implies the conservation of linear momentum. The momentum conservation requires the equal and opposite reaction. CONCLUSION: So, basically there is a confusion in our namings about 1st, 2nd and 3rd law. All of them shows the same thing, conservation of linear momentum. So, in all three dashes we can put inertia, conservation of linear momentum or every action has an equal and opposite reaction.