1. Calculate F, needed to lift a 5250.0 kg car if the area of the platform holding the car (A. is 25.0 times bigger than A;. If A, depresses 1.5 meters, how much work was done on the system? How much was the car lifted up? F; Aj Ao- To reservoir Fluid Fo Valve Valve (a) 2010 Pearson Education, Inc.

1. Calculate F, needed to lift a 5250.0 kg car if the area of the platform holding the car (A. is 25.0 times bigger than A;. If A, depresses 1.5 meters, how much work was done on the system? How much was the car lifted up? F; Aj Ao- To reservoir Fluid Fo Valve Valve (a) 2010 Pearson Education, Inc.

Glencoe Physics: Principles and Problems, Student Edition

1st Edition

ISBN:9780078807213

Author:Paul W. Zitzewitz

Publisher:Paul W. Zitzewitz

Chapter10: Work, Energy And Machines

Section: Chapter Questions

Problem 54A

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Similar questions

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Describe the energy transfers and transformations for a javelin, stating from the point at which an athlete picks up the javelin and ending when the javelin is stuck into the ground after being thrown.
What does work on a shuffleboard puck as it slides to rest? Why is the board dusted, and how does this affect work?
. The fastest that a human has run is about 12 m/s. (a) If a pole vaulter could run this fast and convert all of her kinetic energy into gravitational potential energy, how high would she go? (b) Compare this height with the world record in the pole vault.
Ignoring details associated with friction, extra forces exerted by arm and leg muscles, and other factors, we can consider a pole vault as the conversion of an athlete’s running kinetic energy to gravitational potential energy. If an athlete is to lift his body 4.8 m during a vault, what speed must he have when he plants his pole?
Confirm the value given for the kinetic energy of an aircraft carrier in Table 7.1. You will need to look up the definition of a nautical mile (1knot=1nauticalmile/h) .
The person in Figure 7.33 does work on the lawn mower. Under what conditions would the mower gain energy? Under what conditions would it lose energy?
A constant 20-N force pushes a small ball in the direction of the force over a distance of 5.0 m. What is the work done by the force?
. A particular hydraulic pile driver uses a ram with a mass of 1040 kg. If the maximum pile energy is 11,780J, how high must the ram he raised to achieve this value? Assuming it takes 0.62 s for the pile driver’s winch motor to raise the ram at a constant speed to this height, what is the power output by the motor in completing this task? Express your answer in both watts and horsepower.
Integrated Concepts (a) Calculate the force the woman in Figure 7.46 exerts to do a push-up at constant speed, taking all data to be known to three digits. (b) How much work does she do if her center of mass rises 0.240 m? (c) What is her useful power output if she does 25 push-ups in 1 min? (Should work done lowering her body be included? See the discussion of useful work in Work, Energy, and Power in Humans. Figure 7.46 Forces involved in doing push-ups. The woman's weight acts as a force exerted downward on her center of gravity (CG).
The awe-inspiring Great Pyramid of Cheops was built more than 4500 years ago. Its square base, originally 230 m on a side, covered 13.1 acres, and it was 146 m high, with a mass of about 7109 kg. (The pyramid's dimensions are slightly different today due to quarrying and some sagging.) Historians estimate that 20,000 workers spent 20 years to construct it, working 12-hour days, 330 days per year. (a) Calculate the gravitational potential energy stored in the pyramid, given its center of mass is at one-fourth its height. (b) Only a fraction of the workers lifted blocks; most were involved in support services such as building ramps (see Figure 7.45), bringing food and water, and hauling blocks to the site. Calculate the efficiency of the workers who did the lifting, assuming there were 1000 of them and they consumed food energy at the rate of 300 kcal/h. What does your answer imply about how much of their work went into block-lifting, versus how much work went into friction and lifting and lowering their own bodies? (c) Calculate the mass of food that had to be supplied each day, assuming that the average worker required 3600 kcal per day and that their diet was 5% protein, 60% carbohydrate, and 35% fat. (These proportions neglect the mass of bulk and non-digestible materials consumed.) Figure 7.45 Ancient pyramids were probably constructed using ramps as simple machines. (credit: Franck Monnier, Wikimedia Commons)
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