Question

Which of the following physical laws or principles can best be used to analyze the collision between the object and the pendulum bob? Which can best be used to analyze the resulting swing? 1. Newton's first law 2. Newton's second law 3. Newton's third law 4. Conservation of mechanical energy 5. Conservation of momentum

Answer 1

3. Newton's third law

5. Conservation of momentum

Explanation:

Conservation of momentum is mostly used for describing collisions between objects. Here, the type of collision is inelastic collision in which the object when collides with the pendulum bob sticks to it and moves as a combined object. In this process the momentum is conserved.

Let the mass of the pendulum be m1 moving with a velocity v1.

Let the mass of the object be m2 moving with a velocity v2.

Since the momentum is conserved during collision, the equation will be

$m1 v1 + m2 v2 = (m1 + m2) v$

Where, v is the velocity of the combined system.

Conservation of momentum is actually a direct consequence of Newton's third law.

Consider a collision between two objects, object A and object B. When the two objects collide, there is a force on A due to B. However, because of Newton's third law, there is an equal force in the opposite direction, on B due to A

FAB = -FBA

The mechanical energy is not conserved due to the fact that the kinetic energy is not the same before and after the collision.