Chapter 5: Q. 20P (page 208)
A planet orbits a star in an elliptical orbit. At a particular instant the momentum of the planet is , and the force on the planet by the star is . Find and .
Short Answer
and
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Chapter 5: Q. 20P (page 208)
A planet orbits a star in an elliptical orbit. At a particular instant the momentum of the planet is , and the force on the planet by the star is . Find and .
and
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A proton moving in a magnetic field follows the curving path shown in Figure. The dashed circle is the kissing circle tangent to the path when the proton is at location A. The proton is traveling at a constant speed of 7.0 x 105 m/s, and the radius of the kissing circle is 0.08m . The mass of a proton is 1.7 x 10-27kg . Refer to the directional arrows shown at the right in Figure when answering the questions below.

(a) When the proton is at location A, what are the magnitude and direction of , the parallel component of ?
(b) When the proton is at location A, what are the magnitude and direction of , the perpendicular component of ?
A ball of mass 450 g hangs from a spring whose stiffness is . A string is attached to the ball and you are pulling the string to the right, so that the ball hangs motionless, as shown in Figure. In this situation the spring is stretched, and its length is15 cm. What would be the relaxed length of the spring, if it were detached from the ball and laid on a table?

A helicopter flies to the right (in the +xdirection) at a constant speed of 12m/s, parallel to the surface of the ocean. A 900 kgpackage of supplies is suspended below the helicopter by a cable as shown in Figure the package is also traveling to the right in a straight line, at a constant speed of 12 m/s. The pilot is concerned about whether or not the cable, whose breaking strength is listed at 9300 N , is strong enough to support this package under these circumstances.
(a) Choose the package as the system, and draw a free-body diagram.
(b) What is the magnitude of the tension in the cable supporting the package?
(c) Write the force exerted on the package by the cable as a vector.
(d) What is the magnitude of the force exerted by the air on the package?
(e) Write the force on the package by the air as a vector.
(f) Is the cable in danger of breaking?

A child of mass 26kg swings at the end of an elastic cord. At the bottom of the swing, the child's velocity is horizontal, and the speed is 12m/sAt this instant the cord is 4.30mlong.
(a) At this instant, what is the parallel component of the rate of change of the child's momentum?
(b) At this instant, what is the perpendicular component of the rate of change of the child's momentum?
(c) At this instant, what is the net force acting on the child?
(d) What is the magnitude of the force that the elastic cord exerts on the child? (It helps to draw a diagram of the forces.)
(e) The relaxed length of the elastic cord is 4.22m. What is the stiffness of the cord?
A comet orbits a star in an elliptical orbit, as shown in Figure 5.41. The momentum of the comet at locationis shown in the diagram. At the instant the comet passes each location labeled A, B, C, D, E, and F, answer the following questions about the net force on the comet and the rate of change of the momentum of the comet:
(a) Draw an arrow representing the direction and relative magnitude of the gravitational force on the comet by the star.
(b) Iszero to nonzero?
(c) Iszero or nonzero?
(d) Ispositive, negative, or zero?
(e) Iszero or nonzero?
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