the cup

This weekend was my grandpa's 83 birthday. It was actually on friday but we celebrated it on sunday. I went to my cousin JR's house and we had a small party with the family. We ate lots of food, sang happy birthday and ate the cake and ice cream. When I was eating, I was drinking water in a green cup. Some of my cousins and uncles and aunties were watching this show man vs. food. Some of the stuff he ate was so big and greasy looking. After they showed one of the foods, my family reacted to it and all said "eew". I wanted to see what they were so grossed out about. So, without thinking, I put my cup down on the table and hurried to the tv room. But as I started running, I heard my cup fall on the floor. The reason why it fell can easily be explained by physics. In the first picture, the center of mass is supported by the table. But my cup's center of mass wasn't causing it to fall on the floor. The weight of the cup creates a downward force. When it is supported, then there is no lever arm so it can't exert a torque and fall over. But when the cm isn't supported, the lever arm is from the edge of the table to the cm and there is a torque which causes the cup to rotate over. Next time, I need to pay attention and make sure the cm of my cup is fully supported by the table :)

Christmas time =]

During winter break, we got a tree and decorated it with ornaments and lights. While I was putting the ornaments on, I accidentally hit the tree and one of the ornaments fell. These ornaments were my grandma's and they are really old and fragile. Luckily our tree is on a carpeted area so when the ornament fell, it didn't break. But if the ornament had fell on the hard floor, it would have shattered into pieces. I realized that this was totally related to physics. When a net force is applied to an object to change its velocity and momentum, then it is an impulse (J). In physics, there is a formula for impulse J = F x t (impulse= force x time). Impulse also equals change of momentum. The change of momentum of the ornament would be the same on the hard floor and the carpet because the mass is the same and the change in velocity would be the same. The reason why the ornament didn't break was because the time of impact was extended therefore decreasing the force. The carpet was a cushion that increased the time it took for the ornament's velocity to reach zero. Thanks to physics, my grandma's ornament didn't break.