QUESTION 10 A father racing his son has 1/2 the kinetic energy of the son, who has 1/4 the mass of the father. The father speeds up by 1.7 m/s and then has the same kinetic energy as the son. What are the original speeds of the father and the son, respectively? OA.1.4 m/s and 2.8 m/s OB.4.8 m/s and 10.2 m/s OC.4.1 m/s and 11.6 m/s OD.3.3 m/s 11.6 m/s OE. 4.1 m/s and 8.3 m/s noving object is equal to the

QUESTION 10 A father racing his son has 1/2 the kinetic energy of the son, who has 1/4 the mass of the father. The father speeds up by 1.7 m/s and then has the same kinetic energy as the son. What are the original speeds of the father and the son, respectively? OA.1.4 m/s and 2.8 m/s OB.4.8 m/s and 10.2 m/s OC.4.1 m/s and 11.6 m/s OD.3.3 m/s 11.6 m/s OE. 4.1 m/s and 8.3 m/s noving object is equal to the

Physics for Scientists and Engineers, Technology Update (No access codes included)

9th Edition

ISBN:9781305116399

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter7: Energy Of A System

Section: Chapter Questions

Problem 7.9OQ: Bullet 2 has twice the mass of bullet 1. Both are fired so that they have the same speed. If the...

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Suppose a 350-g kookaburra (a large kingfisher bird) picks up a 75-g snake and raises it 2.5 m from the ground to a branch. (a) How much work did the bird do on the snake? (b) How much work did it do to raise its own center of mass to the branch?
Two blocks of masses m and 3m are placed on a frictionless, horizontal surface. A light spring is attached to the more massive block, and the blocks are pushed together with the spring between them (Fig. P9.5). A cord initially holding the blocks together is burned; after that happens, the block of mass 3m moves to the right with a speed of 2.00 m/s. (a) What is the velocity of the block of mass m? (b) Find the systems original elastic potential energy, taking m = 0.350 kg. (c) Is the original energy in the spring or in the cord? (d) Explain your answer to part (c). (e) Is the momentum of the system conserved in the bursting-apart process? Explain how that is possible considering (f) there are large forces acting and (g) there is no motion before-hand and plenty of motion afterward? Figure P9.5
Two children stand on a platform at the top of a curving slide next to a backyard swimming pool. At the same moment the smaller child hops off to jump straight down into the pool, the bigger child releases herself at the top of the frictionless slide. (i) Upon reaching the water, the kinetic energy of the smaller child com-pared with that of the larger child is (a) greater (b) less (c) equal. (ii) Upon reaching the water, the speed of the smaller child compared with that of the larger child is (a) greater (b) less (c) equal. (iii) During their motions from the platform to the water, the average acceleration of the smaller child compared with that of the larger child is (a) greater (b) less (c) equal.
Bullet 2 has twice the mass of bullet 1. Both are fired so that they have the same speed. If the kinetic energy of bullet 1 is K, is the kinetic energy of bullet 2 (a) 0.25K, (b) 0.5K, (c) 0.71K. (d) K, or (e) 2K?
A 3.00-kg object has a velocity (6.00i1.00j)m/s. (a) What is its kinetic energy at this moment? (b) What is the net work done on the object if its velocity changes to (8.00i+4.00j)m/s. (Note: From the definition of the dot product, v2=vv.)
A 60.0-kg athlete leaps straight up into the air from a trampoline with an initial speed of 9.0 m/s. The goal of this problem is to find the maximum height she attains and her speed at half maximum height. (a) What are the interacting objects and how do they interact? (b) Select the height at which the athletes speed is 9.0 m/s as y = 0. What is her kinetic energy at this point? What is the gravitational potential energy associated with the athlete? (c) What is her kinetic energy at maximum height? What is the gravitational potential energy associated with the athlete? (d) Write a general equation for energy conservation in this case and solve for the maximum height. Substitute and obtain a numerical answer. (e) Write the general equation for energy conservation and solve for the velocity at half the maximum height. Substitute and obtain a numerical answer.
Review. You can think of the workkinetic energy theorem as a second theory of motion, parallel to Newtons laws in describing how outside influences affect the motion of an object. In this problem, solve parts (a), (b), and (c) separately from parts (d) and (e) so you can compare the predictions of the two theories. A 15.0-g bullet is accelerated from rest to a speed of 780 m/s in a rifle barrel of length 72.0 cm. (a) Find the kinetic energy of the bullet as it leaves the barrel. (b) Use the workkinetic energy theorem to find the net work that is done on the bullet. (c) Use your result to part (b) to find the magnitude of the average net force that acted on the bullet while it was in the barrel. (d) Now model the bullet as a particle under constant acceleration. Find the constant acceleration of a bullet that starts from rest and gains a speed of 780 m/s over a distance of 72.0 cm. (e) Modeling the bullet as a particle under a net force, find the net force that acted on it during its acceleration. (f) What conclusion can you draw from comparing your results of parts (c) and (e)?
(a) Sketch a graph of the potential energy function U(x)=kx2/2+Aex2 where k , A, and are constants. (b) What is the force corresponding to this potential energy? (c) Suppose a particle of mass in moving with this potential energy has a velocity v when its position is x = . Show that the particle does not pass 2+2 through the origin unless Amv2=k22(1e a 2 ) .
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. An archer using a simple bow exerts a force of 180 N to draw back the bow string 0.50 m. (a) What is the average work done by the archer in preparing to launch her arrow? (Hint: Compute the average work as you would any average quantity: average work = [final work - initial work].) (b) If all the work is converted into the kinetic energy of the arrow upon its release, what is the arrow's speed as it leaves the bow? Assume the mass of the arrow is 0.021 kg and ignore any kinetic energy in the bow as it relaxes to its original shape. (c) If the arrow is shot straight up, what is the maximum height achieved by the arrow? Ignore any effects due to air resistance in making your assessment.
A 60.0-kg athlete leaps straight up into the air from a trampoline with an initial speed of 9.0 m/s. The goal of this problem is to find the maximum height she attains and her speed at half maximum height. (a) What are the interacting objects and how do they interact? (b) Select the height at which the athletes speed is 9.0 m/s as y = 0. What is her kinetic energy at this point? What is the gravitational potential energy associated with the athlete? (c) What is her kinetic energy at maximum height? What is the gravitational potential energy associated with the athlete? (d) Write a general equation for energy conservation in this case and solve for the maximum height. Substitute and obtain a numerical answer. (e) Write the general equation for energy conservation and solve for the velocity at half the maximum height. Substitute and obtain a numerical answer.
Professional Application Football coaches advise players to block, hit, and tackle with their feet on the ground rather than by leaping through the air. Using the concepts of momentum, work, and energy, explain how a football player can be more effective with his feet on the Ground.