# Explain what isuniversalabout the law of universal gravitation.

Explain what is universal about the law of universal gravitation.

In Discussion Forum 3, post your response to the following discussion questions. Reply to at least two classmates’ responses by the date indicated in the Course Calendar.

• One of your friends says that astronauts in orbit are weightless because they are beyond the pull of Earth’s gravity. Do you agree with your friend?
• An astronaut lands on a planet that has the same mass at the Earth but twice the diameter. How would the weight of the astronaut differ from the weight on Earth?
• If a piece of an airplane suddenly becomes detached during flight, it will crash to Earth. Would it happen the same to a piece of satellite in orbit?
• When a satellite is placed into a higher orbit, what happens to its period?

Written Assignment 5

Answer all of the following questions. Do not send in a partially completed assignment. Answer each question as completely as possible, but do not merely copy answers from your reading materials. If you cite a reference in the text, explain the meaning of the citation.

1. Explain what is universal about the law of universal gravitation.

1. As far as Newton was concerned, what did a falling apple have in common with the moon?

1. Gravitational force acts on all bodies in proportion to their masses. Why, then, doesn’t a heavy body fall faster than a light body?

1. State and explain the implications of each of Kepler’s three laws of planetary motion.

1. Many people mistakenly believe that astronauts that orbit the Earth are “above gravity.” Calculate the acceleration due to gravity (g) for space shuttle territory, 200 kilometers above the Earth’s surface. Earth’s mass is 6 x 1024kilograms and its radius is 6.38 x 106 meters (6380 kilometers). Your answer is what percentage of 9.8m/s2?

1. Why does the force of gravity change the speed of a satellite in an elliptical orbit?

1. What are the restrictions on the orbit of a communications satellite if it is to appear motionless in the sky as viewed from any location on earth?

1. A projectile is launched upward at an angle. What should this angle be with respect to the horizontal in order for the projectile to travel the farthest distance? Explain why.

Lab Exercise 5: Centripetal Acceleration

• Follow the instructions and directions below for this lab.  Disregard the outline in the manual for your LabPaq Kit.
• Do not forget to record your measurements and partial results.
• Submit a Laboratory Report through Moodle, as shown in the last section of this outline.  Remember that the Laboratory Report should include the answers to the questions below.

GOALS

(1) To calculate the angular velocity of a spinning object using varying hanging and rotational masses and varying radii

(2) To calculate the theoretical centripetal force;

(3) To calculate the experimental centripetal force.