13.1 Gravity: A Force of Attraction
Since gravitational force is related to the mass of objects, and the sun is 300,000 bigger than the Earth, why don't you keep moving toward the sun when you jump on a pogo stick?
Gravitational force also depends on the distance between the objects. As the distance between two objects gets larger, the force of gravity gets much smaller.
Why don't you notice the gravity between you and a book?
The book's mass and your mass are both small. The force of gravity caused by a small mass is not large enough to move either you or the book.
What does the law of universal gravitation say about gravity?
The force of gravity depends on the mass of the objects and their distance from each other.
Why was walking on the moon's surface a very bouncy experience for the Apollo astronauts?
The moon has less gravity than the Earth.
Why do static objects not move downward if gravity is pulling on them?
They are balanced by an upward force
Why is the word "universal" used in Newton's law of universal gravitation?
Universal is used because the law applies to all objects.
What balances the force of gravity pulling on a framed picture hanging from a nail on a wall?
tension pulls the picture upward toward the nail
What SI unit is used to express weight?
the newton (N)
What does the sun's gravitational force have a great effect on? Why?
the planets because the mass of the planets is much bigger
How is mass measured?
using a pan balance
How is weight measured?
using a spring scale
What is gravity?
A force of attraction, or a pull, between objects that is due to their masses.
What is mass?
A measure of the amount of matter in an object.
What is weight?
A measure of the gravitational force on an object.
What kinds of matter has mass?
All matter has mass
How are an apple and the moon similar?
An unbalanced force on the moon keeps it moving around the Earth (gravity's pull) just like an unbalanced force causes an apple to fall to the ground.
What is static?
Term used to describe an object that is not moving but on which gravity is acting
Gravity is a result of what?
Mass
What holds objects in the solar system together?
gravity
What SI unit can be used to express mass?
kilograms (kg) or grams (g)
