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  1. Every time I get groceries with my mom I try to bring all of them in the house at once. She typically says, "You should take more trips!" But physics is on my side. It requires more work to bring in several loads of groceries opposed to just one big load. If work is a force x a distance than one big trip will require the least amount of work. To make one big load requires me to move the huge load of groceries, and myself once from the car into my house and into the kitchen. Simply taking two trips would require me to move myself from the car twice and back out to the car once. Splitting the groceries into two loads requires the exact same amount of work to move the groceries once because the force is halved but the distance is doubled. The issue of splitting the groceries into two or more loads is the work required to move myself is added. If assumed the distance is 20 meters from my house to the car and the groceries weigh about 100 kilograms then the force of the groceries is 1000N. The work required to move the groceries 20 meters is about 20,000 J. I weigh about 80 kilograms then the force of gravity is about 800N so it takes about 16000J to move myself. One trip of groceries would be 20,000 J + 16,000 J = 36,000J. Two trips would be 10,000 J(half the groceries) + 16,000 J + 16,000 J + 10,000 J +16,000J = 68,000 J. This is because I must move myself with the groceries 20 meters, then myself back to the car, then myself back inside with groceries again. By doing all of the work in one load I save 32,000 J of energy. Regardless of the load of groceries one big trip would save 32,000 J of work. It may be too difficult to carry all of the groceries at once but a load weighing perhaps weighing 20 kilograms is definitely manageable and effective in conserving energy if all done at once.
  2. Their is a lot of physics in throwing a discus. A throwers body must move in a certain way to provide the maximum power to throw the disc. Throwers must spin to create centripetal acceleration and land in a way to wind up their hips. The hips act like a spring and the thrower pivots his/hip as fast as possible to launch the disc. Not only is power a factor but releasing a disc correctly is extremely important. The disc should be released at a 45 degree angle from the thrower. The disc itself must not be angled at 45 degrees so the thrower must raise his arm at a 45 degree angle to maximize distance and have the discus travel in the air at a 45 degree parabolic path. The thrower must also release the disc as flat as possible so wind provides very little backward force. A disc thrown perpendicular to the ground will fall very quickly because the force of air on the disc will be much greater over an area of an up and down disc as opposed to a sideways disc. With all of the proper technique a discus can be thrown over 200 feet. The world record is 74.08 meters (243 feet). This requires almost perfect form, and training but the art of throwing a disc is based completely on physics.
  3. Typically before a drag race the drivers will spin their tires really fast. This converts Kinetic energy (the movement of the tires) into thermal energy from the friction the ground provides. The tire then is very hot and sticks to the racetrack very well. When the light goes green the friction between the ground and the tire is much greater than if the tire was cold because the hot tire expands and pushes into small bumps In the asphalt much more. The car can launch much easier and convert the kinetic energy of the tires movement into kinetic energy to actually move the car instead of spinning the tires and losing time. This is also typically why drag cars have thicker axles. If the tires don't spin a lot of force from the powerful engine will try to spin the axle and push the 3000 pound car very fast. A very thin axle will snap under the force so a good drag car typically needs a bigger, stronger axle as well.
  4. Back in the 1950's cars weren't made with crumple zones. Cars were made with very simple, straight sheets of steel that weren't made to bend when they crash. So in certain situations ,like fender benders, these cars are great because the fenders won't bend and will break parts on the other car. However if someone smashes into a telephone pole the car won't provide a great enough impulse for a good chance of survival. In the 1970's the growing concern for car safety led to car companies creating cars with what are known as "crumple zones." These are areas made to bend so if a car smashes into a telephone pole the time a person has to experience the massive force is a few fractions of a second greater than before. This may not seem like a lot of time but such a massive force being extended just a little bit longer will have a huge impact and possibly a chance of survival in a massive collision. The acceleration the driver or passenger in the car experiences is significantly smaller. This is also a reason that seatbelts are required. A hard collision at a high-speed in a car without a seatbelt will cause such a massive acceleration to the driver that he/she will fly into (or possibly through) the windshield. Physics helped make cars significantly safer over the past 50 years.
  5. I had to babysit my younger sister and she wanted to watch Monsters Inc. Although the movie's plot may not be the most realistic the physics concepts of the movie are realistic. If you haven't seen the movie children's screams and laughs power doors so when a child laughs they can open up a door to the human universe. A scene included the main characters, Mike and Sully, having their door fall from very high up. Sully is a very big monster and Mike is very small but they both fall at the same speed as each other and the door. Although the weight of Mike, Sully, and the door is probably very different they all accelerate toward the ground at the same speed. This is demonstrated very clearly as the door falls sideways Mike manages to grab the handle and pull himself inside. Mike then musty pull Sully inside and add an additional force other than gravity so Sully accelerates at a greater rate into the door. This scene can help teach young kids physics and is sure to have sparked questions from parents. When my sister grows older I can explain this scene to her and give her a better understanding of gravity.
  6. Opening a tightly sealed pickle-jar can be tricky. There is a logical Physics explanation why running it under hot water can make it easier to open. If we assume it is your average glass pickle-jar with a metal top than heating up the jar will loosen the lid because the metal conducts more heat than the glass. This means the metal will expand before the glass gets the chance to expand the same distance, so as the metal expands the Force required to open the jar decreases. This may seem confusing because the coefficient of glass and metal doesn't change from simply heating it up; but the force of friction is equal to the coefficient of friction x the normal force between the objects. As the lid loosens the normal force the glass produces to push back on the lid is decreased so the Frictional force is lowered. Running the lid under hot water may make your hands slip easier as well because the wet metal on your hand might have a different coefficient of friction, so drying the lid and your hands is recommended.
  7. Walking into a wall or a doorway and hitting your toe can be very painful. Their is a logical explanation for this pain. Walking requires a lot of energy because to walk you must produce friction with the ground with your legs. People swing their legs forward to take another step. When you swing your leg out into a wall and hit your toe, all of the force from the swing goes directly into your toe. It isn't the force that you supply that hurts your toe but the force the wall exerts back on you when you hit it. All of the force that you provide comes back into your toe and tests the strength of the bones in your toe. If enough force is put into the swing, the same amount of force will be exerted into your toe when you hit the wall and break your toe. After hitting my toes many times I've learned to slow down in my house.
  8. When sitting in a chair a lot of forces are acting on each other. As I sit in a chair the force of gravity multiplied by my mass determines the force acting on the chair. Although it seems I am only supplying a force onto the chair, the chair is supplying an equal, opposite force up on me to keep me from moving down. If the chair was not supplying a normal force back on me I would accelerate downwards to the ground at 9.81 m/s. The chair I am sitting in also supplies a force on the ground. The ground must supply a force equal to the weight of me and the chair to keep us from going downward. The normal force holding me and the chair up cannot be greater than the force me and the chair produce because if it did me and the chair would accelerate up into the roof.
  9. One time last year the anchor for the chain I attach my dog's chain to broke. To keep my dog from running away we attached the chain to a heavy metal ladder. What we didn't consider was my dog weighs upward of 100 lbs. My dog produced a large enough force to drag the heavy ladder across the ground. Friction made it difficult for my dog to drag the ladder because to initiate the movement of the ladder my dog had to break the force of static friction to move the ladder. As my dog kept moving the force required to pull the ladder reduced because there was no longer static friction, it was then kinetic friction which is less forceful. A neighbor later came to the door and asked, "Is that your dog with the ladder on it?"
  10. I was playing catch with a football on the football field and thought about the best angle to throw football. I found that when I threw the football at 45 degrees it travelled the farthest distance. Whenever an object is in the air, neglecting air resistance, the object will fall towards the earth at 9.81 m/s. Launching an object straight up in the air will keep it in the air for the longest time but it wont travel any horizontal distance. Also throwing the ball at 0 degrees above the horizontal wont let the football travel any horizontal distance. The maximum horizontal distance will be at 45 degrees because the football will stay in the air for a good portion of time, while also traveling horizontally.
  11. konneroakes


    While I was roofing over the summer with my dad he would put bundles of shingles up on the asphalt roof. The angle of the roof was about 30 degrees. Friction was keeping the bundles of shingles on the roof. However if they were touched just a little they would slide down the roof a little. If I create a free-body diagram of the bundle of shingles on the roof I find that FNet=mg so Ff- mgsin<=0 so Friction=mg< and the normal force is FN= mgcos<. To find friction coeff. of friction= mgsin</mgcos< so the coefficient of friction was equal to tan<. The angle was 30 degrees so tan30 = .577. Ther coefficient of static friction for the bundle of shingles on the roof was .577.
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