University Physics Volume 1

18th Edition

ISBN: 9781938168277

Author: William Moebs, Samuel J. Ling, Jeff Sanny

Publisher: OpenStax - Rice University

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Textbook Question

Chapter 7, Problem 77P

A man of mass 80 kg runs up a flight of stairs 20 m high in 10 s. (a) how much power is used to lift the man?(b) If the man’s body is 25 % efficient, how much power does he expend?

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Chapter 7, Problem 76P

Chapter 7, Problem 78P

Chapter 7 Solutions

University Physics Volume 1

Ch. 7 - Describe a situation in 4iich a force is exerted...Ch. 7 - A body moves in a circle at constant speed. Does...Ch. 7 - Suppose you throw a ball upward and catch it when...Ch. 7 - Why is it more difficult to do sit-ups while on a...Ch. 7 - As a young man, Tarzan climbed up a vine to reach...Ch. 7 - A particle of m has a velocity of . Is its kinetic...Ch. 7 - One particle has mass mand a second particle has...Ch. 7 - A person drops a pebble of mass m1from a height h,...Ch. 7 - The person shown below does work on the lawn...Ch. 7 - Work done on a system puts energy into it. Work...Ch. 7 - Two marbles of masses mand 2mare dropped from a...Ch. 7 - Compare the work required to accelerate a car of...Ch. 7 - Suppose you are jogging at constant velocity. Are...Ch. 7 - Two forces act to double the speed of a particle,...Ch. 7 - Most electrical appliances are rated in watts....Ch. 7 - Explain, in terms of the definition of power, why...Ch. 7 - A spark of static electricity, such as that you...Ch. 7 - Does the work done in lifting an object depend on...Ch. 7 - Can the power expended by a force be negative?Ch. 7 - How can a 50-W light bulb use more energy than a...Ch. 7 - Work How much work does a supermarket checkout...Ch. 7 - A 75.0-kg person climbs stairs, gaining 2.50 m in...Ch. 7 - (a) Calculate the work done on a 1500-kg elevator...Ch. 7 - Suppose a car travels 108 km at a speed of 30.0...Ch. 7 - Calculate the work done by an 85.0-kg man who...Ch. 7 - How much work is done by the boy pulling his...Ch. 7 - A shopper pushes a grocery cart 20.0 m at constant...Ch. 7 - Suppose the ski patrol lowers a rescue sled and...Ch. 7 - A constant 20-N force pushes a small ball in the...Ch. 7 - A toy cart is pulled a distance of 6.0 m in a...Ch. 7 - A 5.0-kg box rests on a horizontal surface. The...Ch. 7 - A sled plus passenger with total mass 50 kg is...Ch. 7 - Suppose that the sled plus passenger of the...Ch. 7 - How much work does the force do on a particle as...Ch. 7 - How much work is done against the gravitationaI...Ch. 7 - It takes 500 J of work to compress a spring 10 cm....Ch. 7 - A bungee cord is essentially a very long rubber...Ch. 7 - A bungee cord exerts a nonlinear elastic force of...Ch. 7 - Engineers desire to model the magnitude of the...Ch. 7 - A particle moving in the xy -plane is subject to a...Ch. 7 - A particle moves along a curved path...Ch. 7 - Kinetic Energy Compare the kinetic energy of a...Ch. 7 - (a) How fast must a 3000-kg elephant move to have...Ch. 7 - Estimate the kinetic energy of a 90,000-ton...Ch. 7 - Calculate the kinetic energies of (a) a 2000.0-kg...Ch. 7 - A 5.0-kg body has three times the kinetic energy...Ch. 7 - An 8.0-g bullet has a speed of 800 m/s. (a) What...Ch. 7 - (a) Calculate the force needed to bring a 950-kg...Ch. 7 - A car’s bumper is designed to withstand a 4.0-km/...Ch. 7 - Boxing gloves are padded to lessen the force of a...Ch. 7 - Using energy considerations, calculate the average...Ch. 7 - A 5.0-kg box has an acceleration of 2.0m/s2 when...Ch. 7 - A constant 10-N horizontal force is applied to a...Ch. 7 - In the preceding problem, the 10-N force is...Ch. 7 - Compare the work required to stop a 100-kg crate...Ch. 7 - A wagon with its passenger sits at the top of a...Ch. 7 - An 8.0-g bullet with a speed of 800 m/s is shot in...Ch. 7 - A 2.0-kg block starts with a speed of 10 m/s at...Ch. 7 - When a 3.0-kg block is pushed against a massless...Ch. 7 - A small block of mass 200 g starts at rest at A,...Ch. 7 - A small object is placed at the top of an incline...Ch. 7 - When released, a 100-g block slides down the path...Ch. 7 - A 0.22LR-caliber bullet like that mentioned in...Ch. 7 - A sled stalls from rest at the top of a...Ch. 7 - A person in good physical condition can put out...Ch. 7 - What is the cost of operating a 3.00-W electric...Ch. 7 - A large household air conditioner may consume 15.0...Ch. 7 - (a) What is the average power consumption in watts...Ch. 7 - (a) What is the average useful power output of a...Ch. 7 - A 500-kg dragster accelerates from rest to a final...Ch. 7 - (a) How long will it take an 850-kg car with a...Ch. 7 - (a) Fir the useful power output of an elevator...Ch. 7 - (a) How long would it take a 1.50105kg airplane...Ch. 7 - Calculate the power output needed for a 950-kg car...Ch. 7 - A man of mass 80 kg runs up a flight of stairs 20...Ch. 7 - The man of the preceding problem consumes...Ch. 7 - An electron in a television tube is accelerated...Ch. 7 - Coal is lifted out of a mine a vertical distance...Ch. 7 - A girl pulls her 15-kg wagon along a flat sidewalk...Ch. 7 - A typical automobile engine has an efficiency of...Ch. 7 - When jogging at 13 km/h on a level surface, a...Ch. 7 - A cart is pulled a distance D on a flat,...Ch. 7 - Consider a particle on which several forces act,...Ch. 7 - Consider a particle on which several forces act,...Ch. 7 - Consider a particle on which several forces act,...Ch. 7 - Consider a particle on which a force acts that...Ch. 7 - A boy pulls a 5-kg cart with a 20-N force at an...Ch. 7 - A crate of mass 200 kg is to be bright from a site...Ch. 7 - At hokey puck of mass 0.17 kg is shot across a...Ch. 7 - A horizontal force of 20 N is required to keep a...Ch. 7 - A 7.0-kg box slides along a horizontal...Ch. 7 - You are driving your car on a straight road with a...Ch. 7 - A crate is being pushed across a rough floor...Ch. 7 - Suppose a horizontal force of 20 N is required to...Ch. 7 - Grains from a hopper falls at a rate of 10 kg/s...Ch. 7 - A cyclist in a race must climb a 5 hill at a speed...Ch. 7 - Shown below is a 40-kg crate that is pushed at...Ch. 7 - The surface of the preceding problem is modified...Ch. 7 - The force F(x) varies with position, as shown...Ch. 7 - Find the work done by the same force in Example...Ch. 7 - Answer the preceding problem using polar...Ch. 7 - Find the work done by the same force in Example...Ch. 7 - Answer the preceding problem using polar...Ch. 7 - Constant power P is delivered to a car of mass m...Ch. 7 - Suppose that the air resistance a car encounters...Ch. 7 - Consider a linear spring, as in Figure 7.7(a),...

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