Physics Blog 4 "Smooth Sailing"

While returning from Kaneohe on a Sunday afternoon, I saw clear roads! OMG! Clear roads, no joke, but after all, it is Sunday.  During the week, the major highways are packed with people, and it got me thinking, what if there was no friction? If there was no kinetic friction, peoples cars wouldn’t slow down, there would be no stopping, and people would save money on gas.  But, we live in a world where friction is present.  When people are driving down the road along side you, and then suddenly start to fall behind, that is most like kinetic friction acting upon them.  They stopped pressing the accelerator and now no forward force is present.  I say most likely because they could possibly be braking, but for now we will assume they weren't.  When I was driving today, I also felt the force of kinetic friction acting upon the car.  I stopped pressing the accelerator, and the car didn’t seem to have that certain “umph” so it slowed to a stop.  As mentioned above, a person would save money on gas because they would only have to accelerate once to get the car moving and wouldn’t have to keep pressing the gas to keep from slowing down.  Maybe if kinetic friction was not present the roads would be smooth sailing.  

Physics Blog 3 "Penguin Slide"

Today I was walking on the third floor of Weinberg, only wearing socks causing my friction to be lowered.  While sliding across the floor, a very random thought occurred to me.  What if a person was to penguin slide across the floor?  If someone started running and then penguin slid across the hallway, four forces would be acting on the person sliding.  In the forward direction, would be the force the person started with, and in the opposing direction would be the force of friction.  The force bearing down on the person would be the weight of the person, and the force that kept the person from falling through the floor was the normal force.  Towards the end of the hallway, the person would slow down because the force of friction was greater than the forward force.  Then later, while on the way home, I thought about the same situation, except the person was trying to penguin slide on concrete.  The same forces would be acting on the object, but the force of friction would be greater because the concrete is not smooth.