In this week’s Highlight, we’re turning to a classic demonstration of inertia: the lead brick. This one is very popular in classes, though not always with whoever has to carry it around – after all, it's a demonstration whose whole purpose is to be hard to move! Graduate student Naren Manjunath shows us what it’s all about in this video. 

Most people would be surprised to learn that being hit with a hammer may not hurt, but this can be possible because of inertia! A lead brick is a very dense object. It contains lot of mass in a small volume. Since heavier objects have a larger moment of inertia, they require a lot of force to move. The force applied to the lead brick by the hammer is not enough to make it move. The energy of the impact is dissipated as heat and distortion of the lead, but not transferred to your hand. The hammer never comes into contact with your hand and never applies force to your hand. Because of this, getting hit with a hammer doesn’t hurt... just don't miss the brick!