College Physics (10th Edition)
10th Edition
ISBN: 9780321902788
Author: Hugh D. Young, Philip W. Adams, Raymond Joseph Chastain
Publisher: PEARSON
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Chapter 7, Problem 34P
An exercise program. A 75 kg person is put on an exercise program by a physical therapist, the goal being to burn up 500 food calories in each daily session. Recall that human muscles are about 20% efficient in converting the energy they use up into mechanical energy. The exercise program consists of a set of consecutive high jumps, each one 50 cm into the air (which is pretty good for a human) and lasting 2.0 s, on the average. How many jumps should the person do per session, and how much time should be set aside for each session? Do you think that this is a physically reasonable exercise session?
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A 2 kg ball is thrown off a 73 m high cliff with a speed of 4 m/s. How fast (in m/s) is the ball going when it hits the ground?
Use g = 9.8 m/s2.
We are now able to define a mathematical formula for gravitational potential energy.
Near the Earth's surface, the gravitational potential energy of a system consisting of the earth and an object with a mass m is
EP = mgh,
where g is the acceleration of gravity (9.80 m/s2) and h is the height above ground level (positive upward).
Note that the "ground level" could really be any height we choose, because what's really important is the change in potential energy. The difference between two heights always gives the same change in potential energy, regardless of where we set the "zero" of height. In other words, if we find the change in potential energy
ΔEP = EP,f − EP,i,
the final potential energy minus the initial, we have
ΔEP = mghf − mghi = mgΔh.
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Не
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Chapter 7 Solutions
College Physics (10th Edition)
Ch. 7 - A box is pushed across a rough horizontal surface...Ch. 7 - Can the total work done on an object during a...Ch. 7 - True or false? If hydrogen molecules and oxygen...Ch. 7 - An elevator is hoisted by its cables at constant...Ch. 7 - A satellite moves in a circular orbit at a...Ch. 7 - If a projectile is fired upward at various angles...Ch. 7 - A block is initially traveling at a speed vc at...Ch. 7 - An advertisment for a portable electrical a...Ch. 7 - A child can slide down any of the three slides...Ch. 7 - Hydroelectric energy comes from gravity pulling...
Ch. 7 - Does the kinetic energy of a car change more when...Ch. 7 - When you jump from the ground into the air, where...Ch. 7 - Two unequal masses are connected by a massless...Ch. 7 - On your electric bill, you are charged for...Ch. 7 - In Figure 7.42, two blocks with masses mA and mB,...Ch. 7 - A car is initially traveling at a speed of v0....Ch. 7 - A spiral spring is compressed so as to add U units...Ch. 7 - You slam on the brakes of your car in a panic and...Ch. 7 - Consider two frictionless inclined planes with the...Ch. 7 - A brick is dropped from the top of a building...Ch. 7 - Prob. 5MCPCh. 7 - Two identical objects are pressed against two...Ch. 7 - For each of two objects with different masses, the...Ch. 7 - Two objects with unequal masses are released from...Ch. 7 - Spring #1 has a force constant of k, and spring #2...Ch. 7 - Two balls having different masses reach the same...Ch. 7 - A fisherman reels in 12.0 m of line while landing...Ch. 7 - A tennis player hits a 58.0 g tennis ball so that...Ch. 7 - A boat with a horizontal tow rope pulls a water...Ch. 7 - A constant horizontal pull of 8.50 N drags a box...Ch. 7 - A rope is tied to a box and used to pull the box...Ch. 7 - A 128.0 N carton is pulled up a frictionless...Ch. 7 - A factory worker moves a 30.0 kg crate a distance...Ch. 7 - An 8.00 kg package in a mail-sorting room slides...Ch. 7 - A tow truck pulls a car 5.00 km along a horizontal...Ch. 7 - A 60 kg woman steps onto an up-going escalator,...Ch. 7 - A bullet is fired into a large stationary absorber...Ch. 7 - Animal energy. 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Tendons are strong elastic fibers that...Ch. 7 - A certain spring stores 10.0 J of potential energy...Ch. 7 - A 0.5 kg ball is thrown up into the air with an...Ch. 7 - Food calories. The food calorie, equal to 4186 J,...Ch. 7 - A good workout. You overindulged in a delicious...Ch. 7 - An exercise program. A 75 kg person is put on an...Ch. 7 - Tall Pacific Coast redwood trees (Sequoia...Ch. 7 - The total height of Yosemite Falls is 2425 ft. (a)...Ch. 7 - The speed of hailstones. Although the altitude may...Ch. 7 - Prob. 38PCh. 7 - Volcanoes on lo. lo, a satellite of Jupiter, is...Ch. 7 - Human energy vs. insect energy. For its size, the...Ch. 7 - A 25 kg child plays on a swing having support...Ch. 7 - A slingshot obeying Hookes law is used to launch...Ch. 7 - A spring with spring constant k is anchored to the...Ch. 7 - A 1.5 kg box moves back and forth on a horizontal...Ch. 7 - A 12.0 N package of whole wheat flour is suddenly...Ch. 7 - A spring of negligible mass has force constant k =...Ch. 7 - A 1.50 kg brick is sliding along on a rough...Ch. 7 - A fun-loving 11.4 kg otter slides up a hill and...Ch. 7 - A 12.0 g plastic ball is dropped from a height of...Ch. 7 - You are rearranging the furniture in your living...Ch. 7 - While a roofer is working on a roof that slants at...Ch. 7 - A block with mass 0.50 kg is forced against a...Ch. 7 - A loaded 375 kg toboggan is traveling on smooth...Ch. 7 - A 62.0 kg skier is moving at 6.50 m/s on a...Ch. 7 - Suppose you were to drop a 14 lb bowling ball from...Ch. 7 - The engine of a motorboat delivers 30.0 kW to the...Ch. 7 - Prob. 57PCh. 7 - A tandem (two-person) bicycle team must overcome a...Ch. 7 - An elevator has mass 600 kg, not including...Ch. 7 - U.S. power use. The total consumption of...Ch. 7 - Solar energy. The sun transfers energy to the...Ch. 7 - A 20.0 kg box is pulled along a rough horizontal...Ch. 7 - A typical flying insect applies an average force...Ch. 7 - When its 75 kW (100 hp) engine is generating full...Ch. 7 - The power of the human heart. The human heart is a...Ch. 7 - At the site of a wind farm in North Dakota, the...Ch. 7 - A physics student measures the energy stored in a...Ch. 7 - Human terminal velocity. By landing properly and...Ch. 7 - A wooden rod of negligible mass and length 80.0 cm...Ch. 7 - Ski jump ramp. You are designing a ski jump ramp...Ch. 7 - Rescue. Your friend (mass 65.0 kg) is standing on...Ch. 7 - On an essentially frictionless horizontal...Ch. 7 - Pendulum. A small 0.12 kg metal ball is tied to a...Ch. 7 - A pump is required to lift 750 liters of water per...Ch. 7 - A 350 kg roller coaster starts from rest at point...Ch. 7 - In action movies there are often chase scenes in...Ch. 7 - In creating his definition of horsepower, James...Ch. 7 - All birds, independent of their size, must...Ch. 7 - A 250 g object on a frictionless, horizontal lab...Ch. 7 - Bungee jump. A bungee cord is 30.0 m long and,...Ch. 7 - Riding a loop-the-loop. A car in an amusement park...Ch. 7 - A 2.0 kg piece of wood slides on the surface shown...Ch. 7 - A 68 kg skier approaches the foot of a hill with a...Ch. 7 - Energy requirements of the body. A 70 kg human...Ch. 7 - The aircraft carrier USS George Washington has...Ch. 7 - A ball is thrown upward with an initial velocity...Ch. 7 - Automotive power. A truck engine transmits 28.0 kW...Ch. 7 - Prob. 88PPCh. 7 - Prob. 89PPCh. 7 - How many times greater is the kinetic energy of...Ch. 7 - During the calibration process, the cantilever is...Ch. 7 - A segment of DNA is put in place and stretched....Ch. 7 - Based on Figure 7.52, how much elastic potential...Ch. 7 - The stage moves at a constant speed while...
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