Newtons law of restitution (experimental law)

Newtons law of restitution (experimental law)

Section 1: Newton’s Law of Restitution

• Understand the concept behind Newton’s Law of Restitution which relates the speed of two objects before and after a collision.
• Know that the law is articulated as e = (v2’-v1’) / (v1-v2), where e is the coefficient of restitution, v1 and v2 are the initial velocities of the two objects (object 1 and 2), and v1’ and v2’ are the final velocities, respectively.
• Comprehend that this equation assumes the motion is along a straight line.

Section 2: Coefficient of Restitution

• Recognise the coefficient of restitution is the ratio of the relative speed after the collision to the relative speed before the collision.
• Grasp that the coefficient of restitution value, e is between 0 and 1 inclusive. A value of e=1 gives an elastic collision where kinetic energy is conserved. A value of e=0 gives an inelastic collision where the two objects stick together and move as one after the collision.

Section 3: Applying the Law

• Be accustomed to applying Newton’s law of restitution to problems involving collision of particles.
• Understand that you may need to consider conservation of momentum and conservation of kinetic energy (if the collision is perfectly elastic) to solve these problems.

Section 4: Useful Tips

• Newton’s law of restitution is often combined with a conservation law (like conservation of momentum) to fully resolve a problem.
• Applying this law usually involves finding the relative speeds before and after the impact.
• Practise plenty of problems involving collisions to master the use of Newton’s law of restitution.