University Physics Volume 1
18th Edition
ISBN: 9781938168277
Author: William Moebs, Samuel J. Ling, Jeff Sanny
Publisher: OpenStax - Rice University
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Chapter 7, Problem 39P
A bungee cord is essentially a very long rubber band that can stretch up to four times its unstretched length. However, its spring constant vanes over its stretch [see Menz, P.G. “The Physics of Bungee Jumping.” The Physics Teacher (November 1993) 31: 483-487]. Take the length of the cord to be along the 
direction and define the stretch 
as the length of the cord 
minus its un-stretched length 
that is, 
(see below). Suppose a particular bungee cord has a spring constant, for 
of 
and for. (Recall that the 
of 
(Recall that the spring constant is the slope of the force 
versus its stretch 
(a) What is the tension in the cord when the stretch is 16.7 m (the maximum desired for a given jump)? (b) How much work must be done against the elastic force of the bungee cord to stretch It 16.7 m?
Figure 7.16 (credit modification of work by Graeme Churchard)
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A bungee cord is essentially a very long rubber band that can stretch up to four times its unstretched length. However, its spring constant varies over its stretch [see Menz, P.G. “The Physics of Bungee Jumping.” The Physics Teacher (November 1993) 31: 483-487]. Take the length of the cord to be along the x-direction and define the stretch x as the length of the cord l minus its un-stretched length l0; that is, x = l − l0 (see below). Suppose a particular bungee cord has a spring constant, for 0 ≤ x ≤ 4.88 m , of k1 = 204 N/m and for 4.88 m ≤ x , of k2 = 111 N/m. (Recall that the spring constant is the slope of the force F(x) versus its stretch x.) (a) What is the tension in the cord when the stretch is 16.7 m (the maximum desired for a given jump)? (b) How much work must be done against the elastic force of the bungee cord to stretch it 16.7 m?
A bungee cord is essentially a very long rubber bandthat can stretch up to four times its unstretched length.However, its spring constant varies over its stretch [seeMenz, P.G. “The Physics of Bungee Jumping.” The PhysicsTeacher (November 1993) 31: 483-487]. Take the length ofthe cord to be along the x-direction and define the stretchx as the length of the cord l minus its un-stretched lengthl0; that is, x = l − l0 (see below). Suppose a particularbungee cord has a spring constant, for 0 ≤ x ≤ 4.88 m , ofk1 = 204 N/m and for 4.88 m ≤ x , of k2 = 111 N/m.(Recall that the spring constant is the slope of the forceF(x) versus its stretch x.) (a) What is the tension in thecord when the stretch is 16.7 m (the maximum desired for agiven jump)? (b) How much work must be done against theelastic force of the bungee cord to stretch it 16.7 m?
A crate of mass m1�1 slides down a well-lubricated hill of height hℎ, with negligible friction. At the bottom, where it is moving horizontally, it collides with another crate, of mass m2, that initially was sitting at rest and that is attached to a wall by a spring of spring constant k that initially is at its equilibrium length. Assume that the spring itself has negligible mass.
a) Write an equation that expresses the speed v of the crate when it arrives at the bottom of the hill in terms of the height of the hill and other known quantities.
b) When the two crates collide, they stick together, due to Velcro pads pasted on their mating surfaces. Write an equation that expresses the speed v2 of the two crates after the collision, in terms of the speed v of crate m1 just before the collision.
c)As the coupled crates continue to move to the right, they compress the spring by a distance d, at which point they momentarily stop. Assuming that the coefficient of kinetic friction between the…
Chapter 7 Solutions
University Physics Volume 1
Ch. 7 - Check Your Understanding Can kinetic friction ever...Ch. 7 - Check Your Understanding Can Earth’s gravity ever...Ch. 7 - Check Your Understanding Find the work done by the...Ch. 7 - Check Your Understanding The spring Example 7.5 is...Ch. 7 - Check Your Understanding (a) A car and a truck...Ch. 7 - Check Your Understanding You are rowing a boat...Ch. 7 - Check Your Understanding suppose the radius of the...Ch. 7 - Check Your Understanding Estimate the power...Ch. 7 - Give an example of something we think of as work...Ch. 7 - Give an example of a situation in which there is a...
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(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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