Which situation describes a body with decreasing potential for energy? a. A boy climbing a tree b. A girl going downstairs c. A boy stretching a horizontal spring d. A pump forcing water upward through a pipe

Which situation describes a body with decreasing potential for energy? a. A boy climbing a tree b. A girl going downstairs c. A boy stretching a horizontal spring d. A pump forcing water upward through a pipe

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter7: Work, Energy, And Energy Resources

Section: Chapter Questions

Problem 10CQ: The force exerted by a diving board is conservative, provided the internal friction is negligible....

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If you run down some stairs and stop, what happens to your kinetic energy and your initial gravitational potential energy?
A 1 000-kg roller coaster car is initially at the top of a rise, at point . It then moves 135 ft, at an angle of 40.0 below the horizontal, to a lower point . (a) Choose the car at point to be the zero configuration for gravitational potential energy of the roller coasterEarth system. Find the potential energy of the system when the car is at points and , and the change in potential energy as the car moves between these points. (b) Repeat part (a), setting the zero configuration with the car at point .
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. The fastest that a human has run is about 12 m/s. (a) If a pole vaulter could run this fast and convert all of her kinetic energy into gravitational potential energy, how high would she go? (b) Compare this height with the world record in the pole vault.
A slingshot consists of a light leather cup containing a stone. The cup is pulled back against two parallel rubber bands. It takes a force of 15.0 N to stretch either one of these bands 1.00 cm. (a) What is the potential energy stored in the two bands together when a 50.0-g stone is placed in the cup and pulled back 0.200 m from the equilibrium position? (b) With what speed does the stone leave the slingshot?
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A flea is able to jump about 0.5 m. It has been said that if a flea were as big as a human, it would be able to jump over a 100-story building! When an animal jumps, it converts work done in contracting muscles into gravitational potential energy (with some steps in between). The maximum force exerted by a muscle is proportional to its cross-sectional area, and the work done by the muscle is this force times the length of contraction. If we magnified a flea by a factor of 1 000, the cross section of its muscle would increase by 1 0002 and the length of contraction would increase by 1 000. How high would this superflea be able to jump? (Dont forget that the mass of the superflea" increases as well.)
A flea is able to jump about 0.5 m. It has been said that if a flea were as big as a human, it would be able to jump over a 100-story building! When an animal jumps, it converts work done in contracting muscles into gravitational potential energy (with some steps in between). The maximum force exerted by a muscle is proportional to its cross-sectional area, and the work done by the muscle is this force times the length of contraction. If we magnified a flea by a factor of 1 000, the cross section of its muscle would increase by 1 0002 and the length of contraction would increase by 1 000. How high would this superflea be able to jump? (Dont forget that the mass of the superflea" increases as well.)
A slingshot consists of a light leather cup containing a stone. The cup is pulled back against two parallel rubber bands. It takes a force of 15.0 N to stretch either one of these bands 1.00 cm. (a) What is the potential energy stored in the two bands together when a 50.0-g stone is placed in the cup and pulled back 0.200 m from the equilibrium position? (b) With what speed does the stone leave the slingshot?
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The launching mechanism of a toy gun consists of a spring of unknown spring constant, as shown in Figure P5.39a. If the spring is compressed a distance of 0.120 m and the gun fired vertically as shown, the gun can launch a 20.0-g projectile from rest to a maximum height of 20.0 m above the starting point of the projectile. Neglecting all resistive forces, (a) describe the mechanical energy transformations that occur from the time the gun is fired until the projectile reaches its maximum height, (b) determine the spring constant, and (c) find the speed of the projectile as it moves through the equilibrium position of the spring (where x = 0), as shown in Figure P5.39b. Figure P5.39