Cars have safety features to protect people during a crash. A bumper is one type of safety feature. Which bumper design do you think is safer?
a bumper that crumples
a bumper that's rigid

Answerthe force between the charges will be  f/9 (one-ninth of force f)explanationcoulomb's law relates the magnitudes  two point charges q₁ and q₂, the distance, r, between the charges, and the electrostatic force, f, between the two charges:     k represents coulomb's constant, k = 8.99×10⁹ n·m²/c².note that if we have r = 3r, then   

Answer mechanical energy;

One answer could be erosion

Conductionhope this .