Honors Physics Work And Energy
Martta
For the rest of this post, I will outline some of the best tips I have for making good use of the diagrams with high school physics students. These are all tweaks or changes that I have made over the past 3 years in the way that I present the diagrams to students.
And the diagram is quantitative in the sense that the total number of blocks in each snapshot does matter. If energy enters the system, there should be more blocks in the subsequent snapshot. If energy leaves, fewer. If there is no total change in energy for the system, then the total number of blocks should be the same in every instant.
In my experience at least, students have a MUCH easier time of things when they write one big equation from their LOL and use it to solve the problem by plugging other details into the One Big Conservation Equation (rather than getting caught up calculating a million tiny things using the little energy formulas all over the place). It helps them organize their approach and not get lost in the details once they start algebra-ing it up.
The hard part of solving any problem should be drawing an accurate and relevant diagram. Turning the diagram into an equation is super easy. Writing an equation with no diagram (or a cursorily drawn one that skips steps) is as hard as drawing the good diagram, except now with bonus difficulties of abstract symbols, easy-to-make sign mistakes, etc. So load the physics into the diagram and let the algebra be easy and sort itself out from there.
You ROCK Kelly! These are very helpful, and a little un-nerving to read, since it sometimes (often) points out things that I could have done much better. Your posts are so valuable and I know will help me become a better modeler. Thank you for taking the time to do this.
One suggestion that I have is to show your arrows going into and out of the system as bars with an arrow head on the end. For example in your third diagram the work done by the spring would be a 4-barred arrow going into the system.
Hi Kelly, I was trying out some variations on the situations you mentioned in your post to see if I understood the way the LOL diagram worked. Referring to the thought experiments I described earlier: I did it for the cart-spring system and then could easily take the spring out of the system. I got a bit stuck when I tried to do it with a ball thrown up and the earth outside the system. Maybe the easiest response would be to show me your LOLs for that situation.
Welcome to Honors Physics, an introductory course in algebra-based high school physics designed to provide students a basic understanding of physics principles in the areas of mechanics, work and energy, electricity and magnetism, semiconductors, waves, optics, and modern physics.
For more information, make sure to check out Honors Physics Essentials, an easy-to-read guide to algebra-based introductory physics, featuring more than 500 worked-out problems with full solutions and covering topics such as: kinematics, dynamics, momentum, impulse, gravity, uniform circular motion, rotational kinematics, work, energy, power, electrostatics, circuits, magnetism, microelectronics, waves, sound, optics, thermal physics, fluids, and modern physics.
Introductory mechanics at a more challenging level and the first semester of a sequence for physics majors. Mechanics of particles in one dimension, kinematics, forces, dynamics; particles in two and three dimensions, vectors, curvilinear and oscillatory motion; conservation principles, work, energy, linear momentum, collisions; rotational mechanics, angular momentum, torque and static equilibrium; gravitation and planetary orbits; wave motion, transverse and longitudinal, standing waves.
Renatta Gass is out with her friends. Misfortune occurs and Renatta and her friends find themselves getting a workout. They apply a cumulative force of 1080 N to push the car 218 m to the nearest fuel station. Determine the work done on the car.
Hans Full is pulling on a rope to drag his backpack to school across the ice. He pulls upwards and rightwards with a force of 22.9 Newtons at an angle of 35 degrees above the horizontal to drag his backpack a horizontal distance of 129 meters to the right. Determine the work (in Joules) done upon the backpack.
Lamar Gant, U.S. powerlifting star, became the first man to deadlift five times his own body weight in 1985. Deadlifting involves raising a loaded barbell from the floor to a position above the head with outstretched arms. Determine the work done by Lamar in deadlifting 300 kg to a height of 0.90 m above the ground.
Sheila has just arrived at the airport and is dragging her suitcase to the luggage check-in desk. She pulls on the strap with a force of 190 N at an angle of 35 to the horizontal to displace it 45 m to the desk. Determine the work done by Sheila on the suitcase.
While training for breeding season, a 380 gram male squirrel does 32 pushups in a minute, displacing its center of mass by a distance of 8.5 cm for each pushup. Determine the total work done on the squirrel while moving upward (32 times).
A new conveyor system at the local packaging plan will utilize a motor-powered mechanical arm to exert an average force of 890 N to push large crates a distance of 12 meters in 22 seconds. Determine the power output required of such a motor.
The ski slopes at Bluebird Mountain make use of tow ropes to transport snowboarders and skiers to the summit of the hill. One of the tow ropes is powered by a 22-kW motor which pulls skiers along an icy incline of 14 at a constant speed. Suppose that 18 skiers with an average mass of 48 kg hold onto the rope and suppose that the motor operates at full power.
Lee Ben Fardest (esteemed American ski jumper), has a mass of 59.6 kg. He is moving with a speed of 23.4 m/s at a height of 44.6 meters above the ground. Determine the total mechanical energy of Lee Ben Fardest.
Olive Udadi is at the park with her father. The 26-kg Olive is on a swing following the path as shown. Olive has a speed of 0 m/s at position A and is a height of 3.0-m above the ground. At position B, Olive is 1.2 m above the ground. At position C (2.2 m above the ground), Olive projects from the seat and travels as a projectile along the path shown. At point F, Olive is a mere picometer above the ground. Assume negligible air resistance throughout the motion. Use this information to fill in the table.
Pete Zaria works on weekends at Barnaby's Pizza Parlor. His primary responsibility is to fill drink orders for customers. He fills a pitcher full of Cola, places it on the counter top and gives the 2.6-kg pitcher a 8.8 N forward push over a distance of 48 cm to send it to a customer at the end of the counter. The coefficient of friction between the pitcher and the counter top is 0.28.
The Top Thrill Dragster stratacoaster at Cedar Point Amusement Park in Ohio uses a hydraulic launching system to accelerate riders from 0 to 53.6 m/s (120 mi/hr) in 3.8 seconds before climbing a completely vertical 420-foot hill.
Paige is the tallest player on South's Varsity volleyball team. She is in spiking position when Julia gives her the perfect set. The 0.226-kg volleyball is 2.29 m above the ground and has a speed of 1.06 m/s. Paige spikes the ball, doing 9.89 J of work on it.
According to ABC's Wide World of Sports show, there is the thrill of victory and the agony of defeat. On March 21 of 1970, Vinko Bogataj was the Yugoslavian entrant into the World Championships held in former West Germany. By his third and final jump of the day, heavy and persistent snow produced dangerous conditions along the slope. Midway through the run, Bogataj recognized the danger and attempted to make adjustments in order to terminate his jump. Instead, he lost his balanced and tumbled and flipped off the slope into the dense crowd. For nearly 30 years thereafter, footage of the event was included in the introduction of ABC's infamous sports show and Vinco has become known as the agony of defeat icon.
Nolan Ryan reportedly had the fastest pitch in baseball, clocked at 100.9 mi/hr (45.0 m/s) If such a pitch had been directed vertically upwards at this same speed, then to what height would it have traveled?
In the Incline Energy lab, partners Anna Litical and Noah Formula give a 1.00-kg cart an initial speed of 2.35 m/s from a height of 0.125 m above the lab table. Determine the speed of the cart when it is located 0.340 m above the lab table.
In April of 1976, Chicago Cub slugger Dave Kingman hit a home run which cleared the Wrigley Field fence and hit a house located 530 feet (162 m) from home plate. Suppose that the 0.145-kg baseball left Kingman's bat at 92.7 m/s and that it lost 10% of its original energy on its flight through the air. Determine the speed of the ball when it cleared the stadium wall at a height of 25.6 m.
Dizzy is speeding along at 22.8 m/s as she approaches the level section of track near the loading dock of the Whizzer roller coaster ride. A braking system abruptly brings the 328-kg car (rider mass included) to a speed of 2.9 m/s over a distance of 5.55 meters. Determine the braking force applied to Dizzy's car.
A 6.8-kg toboggan is kicked on a frozen pond, such that it acquires a speed of 1.9 m/s. The coefficient of friction between the pond and the toboggan is 0.13. Determine the distance which the toboggan slides before coming to rest.
Connor (m=76.0 kg) is competing in the state diving championship. He leaves the springboard from a height of 3.00 m above the water surface with a speed of 5.94 m/s in the upward direction.
a. Determine Connor's speed when he strikes the water.
b. Connor's body plunges to a depth of 2.15 m below the water surface before stopping. Determine the average force of water resistance experienced by his body.
Gwen is baby-sitting for the Parker family. She takes 3-year old Allison to the neighborhood park and places her in the seat of the children's swing. Gwen pulls the 1.8-m long chain back to make a 26 angle with the vertical and lets 14-kg Allison (swing mass included) go. Assuming negligible friction and air resistance, determine Allison's speed at the lowest point in the trajectory.
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