If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Course: AP®︎/College Physics 1 > Unit 3

Lesson 7: Applications of circular motion and gravitation
Science
AP®︎/College Physics 1
Circular motion and gravitation
Applications of circular motion and gravitation
© 2024 Khan AcademyTerms of usePrivacy PolicyCookie Notice

Applications of circular motion and gravitation

Google Classroom
You might need: Calculator

Problem

On a planet with no atmosphere and a mass twice that of Earth's, a 12.5kg rock falls off of a cliff. Beginning at an arbitrary time during free fall, the resulting vertical velocity of the rock as a function of time is shown in the graph.
Determine the radius of this planet in terms of Earth radii, RE.
Write your answer to two significant figures.
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3/5
  • a simplified improper fraction, like 7/4
  • a mixed number, like 1 3/4
  • an exact decimal, like 0.75
  • a multiple of pi, like 12 pi or 2/3 pi
RE