University Physics Volume 1 18th Edition
ISBN: 9781938168277
Author: William Moebs, Samuel J. Ling, Jeff Sanny
Publisher: William Moebs, Samuel J. Ling, Jeff Sanny
1 Units And Measurement 2 Vectors 3 Motion Along A Straight Line 4 Motion In Two And Three Dimensions 5 Newton's Law Of Motion 6 Applications Of Newton's Laws 7 Work And Kinetic Energy 8 Potential Energy And Conservation Of Energy 9 Linear Momentum And Collisions 10 Fixed-axis Rotation 11 Angular Momentum 12 Static Equilibrium And Elasticity 13 Gravitation 14 Fluid Mechanics 15 Oscillations 16 Waves 17 Sound Chapter7: Work And Kinetic Energy
Chapter Questions Section: Chapter Questions
Problem 7.1CYU: Check Your Understanding Can kinetic friction ever be a constant force for all paths? Problem 7.2CYU: Check Your Understanding Can Earth’s gravity ever be a constant force for all paths? Problem 7.3CYU: Check Your Understanding Find the work done by the same force in Example 7.4 over a cubic path,... Problem 7.4CYU: Check Your Understanding The spring Example 7.5 is compressed 6 cm from its equilibrium length. (a)... Problem 7.5CYU: Check Your Understanding (a) A car and a truck each moving with the same kinetic energy. Assume that... Problem 7.6CYU: Check Your Understanding You are rowing a boat parallel to the banks of a river. Your kinetic energy... Problem 7.7CYU: Check Your Understanding suppose the radius of the loop-the-loop in Example 7.9 is 15 cm and the toy... Problem 7.8CYU: Check Your Understanding Estimate the power expended by a weightlifter raising a 150-kg barbell 2 m... Problem 1CQ: Give an example of something we think of as work in everyday circumstances that is not work in the... Problem 2CQ: Give an example of a situation in which there is a force and a displacement, but the force does no... Problem 3CQ: Describe a situation in 4iich a force is exerted for a long time but does no work. Explain. Problem 4CQ: A body moves in a circle at constant speed. Does the centripetal force that accelerates the body do... Problem 5CQ: Suppose you throw a ball upward and catch it when it returns at the same height. How much work does... Problem 6CQ: Why is it more difficult to do sit-ups while on a slant board than on a horizontal surface? (See... Problem 7CQ: As a young man, Tarzan climbed up a vine to reach his tree house. As he got older, he decided to... Problem 8CQ: A particle of m has a velocity of . Is its kinetic energy given by ? If not, what is the correct... Problem 9CQ: One particle has mass mand a second particle has mass 2m . The second particle is moving with speed... Problem 10CQ: A person drops a pebble of mass m1from a height h, and it hits the floor with kinetic energy K. The... Problem 11CQ: The person shown below does work on the lawn mower. Under what conditions would the mower gain... Problem 12CQ: Work done on a system puts energy into it. Work done by a system removes energy from it. Give an... Problem 13CQ: Two marbles of masses mand 2mare dropped from a height h. Compare their kinetic energies when they... Problem 14CQ: Compare the work required to accelerate a car of mass 2000 kg from 30.0 to 400 km/h with that... Problem 15CQ: Suppose you are jogging at constant velocity. Are you doing any work on the environment and vice... Problem 16CQ: Two forces act to double the speed of a particle, initially moving with kinetic energy of 1 J. One... Problem 17CQ: Most electrical appliances are rated in watts. Does this rating depend on how long the appliance is... Problem 18CQ: Explain, in terms of the definition of power, why energy consumption is sometimes listed in... Problem 19CQ: A spark of static electricity, such as that you might receive from a doorknob on a cold dry day, may... Problem 20CQ: Does the work done in lifting an object depend on how fast it is lifted? Does the power expended... Problem 21CQ: Can the power expended by a force be negative? Problem 22CQ: How can a 50-W light bulb use more energy than a 1000-W oven? Problem 23P: Work How much work does a supermarket checkout attendant do on a can of sip he pushes 0.600 m... Problem 24P: A 75.0-kg person climbs stairs, gaining 2.50 m in height. Find the work done to accomplish this... Problem 25P: (a) Calculate the work done on a 1500-kg elevator car by its cable to lift it 40.0 m at constant... Problem 26P: Suppose a car travels 108 km at a speed of 30.0 m/s, and uses 2.0 gal of gasoline. Only 30 of the... Problem 27P: Calculate the work done by an 85.0-kg man who pushes a crate 4.00 m up along a ramp that makes an... Problem 28P: How much work is done by the boy pulling his sister 30.0 m in a wagon as shown below? Assume no... Problem 29P: A shopper pushes a grocery cart 20.0 m at constant speed on level ground, against a 35.0 N... Problem 30P: Suppose the ski patrol lowers a rescue sled and victim, having a total mass of 90.0 kg, down a 60.00... Problem 31P: A constant 20-N force pushes a small ball in the direction of the force over a distance of 5.0 m.... Problem 32P: A toy cart is pulled a distance of 6.0 m in a straight line across the floor. The force pulling the... Problem 33P: A 5.0-kg box rests on a horizontal surface. The coefficient of kinetic friction between the box and... Problem 34P: A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (K=0.20) at constant... Problem 35P: Suppose that the sled plus passenger of the preceding problem is pushed 20 m across the snow at... Problem 36P: How much work does the force do on a particle as it moves from to Problem 37P: How much work is done against the gravitationaI force on a 5.0-kg briefcase when it is carried from... Problem 38P: It takes 500 J of work to compress a spring 10 cm. What is the force constant of the spring? Problem 39P: A bungee cord is essentially a very long rubber band that can stretch up to four times its... Problem 40P: A bungee cord exerts a nonlinear elastic force of magnitude where is the distance the cord is... Problem 41P: Engineers desire to model the magnitude of the elastic force of a bungee cord using the equation... Problem 42P: A particle moving in the xy -plane is subject to a force F(x,y)=(50Nm2)(xi+yj)( x 2 + y 2 )3/2 ,... Problem 43P: A particle moves along a curved path y(x)=(10m){1+cos[0.1m1]x} , from x=0 to x=10m , subject to a... Problem 44P: Kinetic Energy Compare the kinetic energy of a 20,000-kg truck moving at 110 km/h with that of an... Problem 45P: (a) How fast must a 3000-kg elephant move to have the same kinetic energy as a 65.0-kg sprinter... Problem 46P: Estimate the kinetic energy of a 90,000-ton aircraft carrier moving at a speed of at 30 knots. You... Problem 47P: Calculate the kinetic energies of (a) a 2000.0-kg automobile moving at 100.0 km/h; (b) an 80.-kg... Problem 48P: A 5.0-kg body has three times the kinetic energy of an 8.0-kg body. Calculate the ratio of the... Problem 49P: An 8.0-g bullet has a speed of 800 m/s. (a) What is its kinetic energy? (b) What is its kinetic... Problem 50P: (a) Calculate the force needed to bring a 950-kg car to rest from a speed of 90.0 km/h in a distance... Problem 51P: A car’s bumper is designed to withstand a 4.0-km/ h (1.1-m/s) collision with an immovable object... Problem 52P: Boxing gloves are padded to lessen the force of a blow. (a) Calculate the force exerted by a boxing... Problem 53P: Using energy considerations, calculate the average force a 60.0-kg sprinter exerts backward on the... Problem 54P: A 5.0-kg box has an acceleration of 2.0m/s2 when it is pulled by a horizontal force across a surface... Problem 55P: A constant 10-N horizontal force is applied to a 20-kg cart at rest on a level floor. If friction is... Problem 56P: In the preceding problem, the 10-N force is applied at an angle of 45 below the horizontal. What is... Problem 57P: Compare the work required to stop a 100-kg crate sliding at 1.0 m/s and an 8.0-g bullet traveling at... Problem 58P: A wagon with its passenger sits at the top of a hill. The wagon is given a slight push and rolls 100... Problem 59P: An 8.0-g bullet with a speed of 800 m/s is shot in to a wooden block and penetrates 20 cm before... Problem 60P: A 2.0-kg block starts with a speed of 10 m/s at the bottom of a plane inclined at 37 to the... Problem 61P: When a 3.0-kg block is pushed against a massless spring of force constant constant 4.5103N/m , the... Problem 62P: A small block of mass 200 g starts at rest at A, slides to B where its speed is then slides along... Problem 63P: A small object is placed at the top of an incline that is essentially frictionless. The object... Problem 64P: When released, a 100-g block slides down the path shown below, reaching the bottom with a speed of... Problem 65P: A 0.22LR-caliber bullet like that mentioned in Example 7.10 is fired into a door made of a single... Problem 66P: A sled stalls from rest at the top of a snow-covered incline that makes a 22 angle with the... Problem 67P: A person in good physical condition can put out 100 W of useful power for several hours at a... Problem 68P: What is the cost of operating a 3.00-W electric clock for a year if the cost of electricity is... Problem 69P: A large household air conditioner may consume 15.0 kW of power. What Is the cost of operating this... Problem 70P: (a) What is the average power consumption in watts of an appliance that uses 5.00kWh of energy per... Problem 71P: (a) What is the average useful power output of a person who does 6.00106J of useful work in 8.00 h?... Problem 72P: A 500-kg dragster accelerates from rest to a final speed of 110 m/s in 400 m (about a quarter of a... Problem 73P: (a) How long will it take an 850-kg car with a useful power output of 40.0 hp (1 hp equals 746 W) to... Problem 74P: (a) Fir the useful power output of an elevator motor that Lifts a 2500-kg load a height of 35.0 m in... Problem 75P: (a) How long would it take a 1.50105kg airplane with engines that produce 100 MW of power to reach a... Problem 76P: Calculate the power output needed for a 950-kg car to climb a 2.00 slope at a constant 30.0 m/s... 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... Problem 78P: The man of the preceding problem consumes approximately 1.05107J (2500 food calories) of energy per... Problem 79P: An electron in a television tube is accelerated uniformly from rest to a speed of 8.4107 m/s over a... Problem 80P: Coal is lifted out of a mine a vertical distance of 50 m by an engine that supplies 500 W to a... Problem 81P: A girl pulls her 15-kg wagon along a flat sidewalk by applying a 10-N force at 37 to the horizontal.... Problem 82P: A typical automobile engine has an efficiency of 25 . Suppose that the engine of a 1000-kg... Problem 83P: When jogging at 13 km/h on a level surface, a 70-kg man uses energy at a rate of approximately 850... Problem 84AP: A cart is pulled a distance D on a flat, horizontal surface by a constant farce F that acts at an... Problem 85AP: Consider a particle on which several forces act, one of which is known to be constant in time: . As... Problem 86AP: Consider a particle on which several forces act, one of which is known to be constant in time: . As... Problem 87AP: Consider a particle on which several forces act, one of which is known to be constant in time: . As... Problem 88AP: Consider a particle on which a force acts that depends on the position of the particle. This force... Problem 89AP: A boy pulls a 5-kg cart with a 20-N force at an angle of 30 above the horizontal for a length of... Problem 90AP: A crate of mass 200 kg is to be bright from a site on the ground floor to a third floor apartment.... Problem 91AP: At hokey puck of mass 0.17 kg is shot across a rough floor with the roughness different at different... Problem 92AP: A horizontal force of 20 N is required to keep a 5.0 kg box traveling at a constant speed up a... Problem 93AP: A 7.0-kg box slides along a horizontal frictionless floor at 1.7 m/s and collides with a relatively... Problem 94AP: You are driving your car on a straight road with a coefficient of friction between the tires and the... Problem 95AP: A crate is being pushed across a rough floor surface. If no force is applied on the crate, the crate... Problem 96AP: Suppose a horizontal force of 20 N is required to maintain a speed of 8 m/s of a 50 kg crate. (a)... Problem 97AP: Grains from a hopper falls at a rate of 10 kg/s vertically onto a conveyor belt that is moving... Problem 98AP: A cyclist in a race must climb a 5 hill at a speed of 8 m/s. If the mass of the bike and the biker... Problem 99CP: Shown below is a 40-kg crate that is pushed at constant velocity a distance 8.0 m along a 30 Incline... Problem 100CP: The surface of the preceding problem is modified so that the coefficient of kinetic friction is... Problem 101CP: The force F(x) varies with position, as shown beolow Find the work done by this force on a particle... Problem 102CP: Find the work done by the same force in Example 7.4, between the same points, A=(0,0) and B=(2m,2m)... Problem 103CP: Answer the preceding problem using polar coordinates. Problem 104CP: Find the work done by the same force in Example 7.4, between the same points, A=(0,0) and B=(2m,2m)... Problem 105CP: Answer the preceding problem using polar coordinates. Problem 106CP: Constant power P is delivered to a car of mass m by its engine. Show that If air resistance can be... Problem 107CP: Suppose that the air resistance a car encounters is independent of its speed. When the car travels... Problem 108CP: Consider a linear spring, as in Figure 7.7(a), with mass M uniformly distributed along its length.... Problem 34P: A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (K=0.20) at constant...
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Concept explainers
A 25kg wagon is pulled by Bill with an applied force of 40N (29 degrees above the horizontal). The force of friction is constant 15N. If the wagon is pulled 15m. Calculate
a. The work done by Bill.
b. The work done by friction
c. The net work.
Definition Definition Force that opposes motion when the surface of one item rubs against the surface of another. The unit of force of friction is same as the unit of force.
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