-Gravitational Forces.pdf - Gravitational Forces Have you ever wondered what keeps our feet on the ground You might have learned the answer the force of

# -Gravitational Forces.pdf - Gravitational Forces Have you...

• Notes
• 6

This preview shows page 1 - 3 out of 6 pages.

1 DYr^vP[t^[tPVoUn^S )VoYr`LZs Have you ever wondered what keeps our feet on the ground? You might have learned the answer: the force of gravity does. What keeps Earth moving around the Sun? Gravity does. What keeps the Moon moving around Earth? Again, gravity does. In fact, the force that makes this cup and saucer fall to the ground is the same force that keeps the Moon and Earth in orbit. How can gravity do all that? What is gravitational force? ,rIFvQNity% '&Sn '&ttrIFKHctQNivMJe +TorKHcMJe ('MJetwMJeMJeSn 23IFssMJes What is gravity? Physics uses four fundamental forces to explain the motions of objects in the universe. Gravity is one of these forces. You may already know about gravity from everyday experience. It is the force that draws you back to the ground when you jump. Dr^vLty is an attractive force between all objects with mass. What is an attractive force? It is a force between two objects that pulls the objects toward each other. The force of gravity attracts you toward Earth when you jump, because both you and Earth have mass. The force of gravity also pulls Earth and the Sun toward each other, as well as Earth and the Moon, Mars, and all the other planets in the solar system. (Each of these bodies also has its own momentum, which balances the force of gravity. If it were not for momentum, gravity would cause these bodies to crash into each other, and if it were not for gravity, momentum would cause these bodies to ﬂy apart. Instead, Earth and the planets orbit the Sun, and the Sun revolves around the center of the Milky Way galaxy.) Although you don’t feel it, gravity even attracts you to your computer, your chair, the people in the room around you, and everything else that has mass. Why don’t you feel these other gravitational forces? The force of gravity on you from Earth has a much greater strength, so you do not notice the other pulls. Two objects with mass exert a gravitational pull on each other. The force on one of the objects in the pair has the same m^JnLtuGH , or strength, as the force on the other object, but it points in the opposite direction. The force on the ﬁrst object points toward the second object. The force on the second object points toward the ﬁrst object. Both objects feel the same magnitude of force. This fact means that Earth feels the same magnitude of gravitational force toward you as you do toward Earth! The force of gravity near the Moon’s surface has been carefully measured by satellites in NASA’s GRAIL mission. This color-coded image of the Moon shows the results. The force of gravity is stronger in the red areas and weaker in the blue areas.
2 DYr^vP[t^[tPVoUn^S )VoYr`LZs The force of gravity reaches everywhere, even into space. You may have seen videos of

#### You've reached the end of your free preview.

Want to read all 6 pages?

• Spring '16
• Steven

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern