Chp. 7 Outline: Circular Motion and Gravity
Chp. 7 Outline: Circular Motion and Gravity
Lecture Questions:
1)Distinguish between a rotation and a revolution. Give some examples of each. Which does this chapter discuss?
2)Define angular distance, angular velocity and angular acceleration.. What are some units used to measure these quantities? What conversion factors relate these quantities to their linear counterparts? Which quantities vary with radius on a spinning turntable?
3)What is required for an object to travel in a circle? How is a centripetal force affect the speed of an object? Describe the path of an object traveling in a circle that suddenly loses its centripetal force. What force is providing the centripetal force in the following circumstances: a) ball whirled in horizontal circle on string; b) Moon orbiting Earth: c) car moving around banked curve.
4)How does the centripetal force required to keep an object moving in a circular path vary with the linear speed of the object and radius of curvature of the turn? Write Newton’s second law for an object in circular motion.
5)What is centrifugal force? Why is this force often called a false force? What is the true cause of the centrifugal force you feel when you car rounds a curve?
6) Explain how centripetal force is used to simulate gravity on a rotating space station. How does the artificial gravity vary as you move to the center of the station?
7)What did Newton prove about the force on a falling apple and the force of the Earth on the Moon? How did he do this? What is universal about gravity?
8)Write the Law of Universal gravitation verbally and mathematically. Define all variables and constants. In which direction is the force?
9)How will the gravitational force between two objects change if the following changes are made: a) one of the masses double b) both masses double c) the distance between the masses is halved d) the distance between the masses is tripled e) one mass is doubled and the distance between the masses is tripled?
10)How does little g differ from big G in terms of where they are constants and how they are measured? Explain why gravity exhibits the inverse square law with distance?
11)How does a mass change the space around it? Is gravity a contact or action at a distance force? What two variables change the gravitational field around an object? Which one does not? Write the equation for the gravitational field around an object.
12)Draw a graph showing the gravitational field both inside and outside the Earth. Where is this field the strongest? Where is this field the weakest?
13)When will an object exhibit apparent weightlessness? Why does an astronaut appear weightless as she circles the Earth in the space shuttle or other spacecraft?
14)What causes the tides on Earth? Draw the configuration of the Moon, Earth and Sun during a neap tide. Do the same during a leap tide. Describe the relative heights of the high and low tides for each.
15)State Kepler’s three laws of planetary motion. In an elliptical orbit state where the following quantities are greatest: a) kinetic energy b) potential energy c) speed d) centripetal acceleration e) tangential acceleration ? How do these quantities compare for a circular orbit? Write the equation for finding the tangential speed of a particular circular orbit? Write the equation for the period of such an orbit.
16)How is a black hole created? How does the gravitational field of the black hole compare to that of the star that created it?
17)What two observations about galaxy motion suggests the Big Bang origin for the universe? Distinguish between an open and closed universe. Which do we have?
Schedule:
Date:Class Activity:Homework Due:
MondayLab: Centripetal Force StationsNone
TuesdayLecture: Circular Motion (Q 1-6) None
WednesdayProblem Day (Q 1-11)None
ThursdayNTQ and HW ReviewChp. 7, 1-5, 6,8,10,
12,14-21,22,24,26-34, 36,38
FridayPSSC Circular Motion LabNone
MondayLecture: Universal Gravitation (Q 7-10)None
TuesdayLecture: Gravitational Fields (Q 11-13)None
WednesdayLecture: Gravitational Interactions (Q. 14-17)None
ThursdayNTQ and HW ReviewHandout
FridayChapter 7 QuizNotebook
Practice Problems:
1)A cave dweller rotates a pebble in a sling with a radius of .30 m counterclockwise through an arc length of 0.96 m. What is the angular displacement of the pebble?
2)What is the approximate angular speed of a wheel rotating at the rate of 5.0 rev/s?
3)A grinding wheel initially at rest with a radius of 0.15 m rotates until it reaches an angular speed of 12.0 rad/s in 4.0 s. What is the wheel’s average angular acceleration?
4)A Ferris wheel rotates with an initial angular speed of 0.50 rad/s and accelerates over a 7.00 s interval at a rate of 4.0 x 10-2 rad/s2. What is its final angular speed?
5)An automobile tire with a radius of 0.30 m starts at rest and accelerates at an angular speed of 2.0 rad/s2 for 5 s. What is the angular displacement of the tire?
6)A gear in a machine accelerates at 11.2 rad/s2. If the wheel’s initial angular speed is 5.40 rad/s, what is the wheel’s angular speed after exactly three full turns?
7)The end of the cord on a weed cutter is 0.15 m in length. If the motor rotates at the rate of 126 rad/s, what is the tangential speed of the cord?
8)A cylinder with a diameter of .150 m rotates in a lathe at a constant angular speed of 35.6 rad/s. What is the tangential speed of the surface of the cylinder?
9)An automobile tire with a radius of 0.3 m accelerates from rest at a constant 2 rad/s2 over a 5 s interval. What is the tangential component of acceleration of the wheel’s edge?
10)A lapidary plate at rest is turned on to cut a gemstone. The plate rotates until it reaches an angular speed of 12.0 rad/s in 4.0 s. What is the centripetal acceleration of a point 0.10 m from the center of the plate?
11)A 0.40 kg ball on a 0.50 m string rotates in a circular path in a vertical plane. If the angular speed of the ball at the bottom of the circle is 8.0 rad/s, what is the tension in the string at this point? What is the tension in the string if the ball is at the top of the circle?
AP Supplemental Assignment:
Giancoli Chp. 5 Pbs. 9,13,15,25,29,33,39,47 (Due R before quiz)
Revised 10/25/2018