Chapter 5: Q20P (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 role="math" localid="1654057870125" .
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Chapter 5: Q20P (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 role="math" localid="1654057870125" .
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A circular pendulum of length 1.1 mgoes around at an angle of 28 degreesto the vertical. Predict the speed of the mass at the end of the string. Also predict the period, the time it takes to go around once. Remember that the radius of the circle is the length of the string times the sine of the angle that the string makes to the vertical.
P49 The Ferris wheel in Figure 5.80is a vertical, circular amusement ride with radius 10m . Riders sit on seats that swivel to remain horizontal. The Ferris wheel rotates at a constant rate, going around once in 10.5s. Consider a rider whose mass is 56kg .
(a) At the bottom of the ride, what is the rate of change of the rider's momentum? (b) At the bottom of the ride, what is the vector gravitational force exerted by the Earth on the rider?
(c) At the bottom of the ride, what is the vector force exerted by the seat on the rider?
(d) Next consider the situation at the top of the ride. At the top of the ride, what is the rate of change of the rider's momentum?
(e) At the top of the ride, what is the vector gravitational force exerted by the Earth on the rider?
(f) At the top of the ride, what is the vector force exerted by the seat on the rider?
A rider feels heavier if the electric, interatomic contact force of the seat on the rider is larger than the rider's weight mg (and the rider sinks more deeply into the seat cushion). A rider feels lighter if the contact force of the seat is smaller than the rider's weight (and the rider does not sink as far into the seat cushion).
(g) Does a rider feel heavier or lighter at the bottom of a Ferris wheel ride?
(h) Does a rider feel heavier or lighter at the top of a Ferris wheel ride?

A block with mass 0.4 kgis connected by a spring of relaxed length 0.15 mto a post at the centre of a low-friction table. You pull the block straight away from the post and release it, and you observe that the period of oscillation is 0.6 s. Next you stretch the spring to a length of 0.28mand give the block an initial speed vperpendicular to the spring, choosing vso that the motion is a circle with the post at the centre. What is this speed?
The angle between the gravitational force on a planet by a star and the momentum of the planet is at a particular instant. At this instant the magnitude of the planet’s momentum isrole="math" localid="1654013162020" , and the magnitude of the gravitational force on the planet is role="math" localid="1654013174728" . (a) What is the parallel component of the force on the planet by the star? (b) What will be the magnitude of the planet’s momentum after 8h?
Tarzan swings back and forth on a vine. At the microscopic level, why is the tension force on Tarzan by the vine greater than it would be if he were hanging motionless?
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