4.14. Gravity http://www.ck12.org
Gravity and Weight
Weight measures the force of gravity pulling downward on an object. The SI unit for weight, like other forces, is the
Newton (N). On Earth, a mass of 1 kilogram has a weight of about 10 Newtons because of the pull of Earth’s gravity.
On the moon, which has less gravity, the same mass would weigh less. Weight is measured with a scale, like the
spring scale shown in theFigure4.28. The scale measures the force with which gravity pulls an object downward.
To delve a little deeper into weight and gravity, watch this video:
http://www.youtube.com/watch?v=HRUhRjqzzDM
FIGURE 4.28
Summary
- Gravity has traditionally been defined as a force of attraction between things that have mass. The strength of
gravity between two objects depends on their mass and their distance apart. - Earth’s gravity constantly pulls matter toward the center of the planet. It also keeps moons and satellites
orbiting Earth and Earth orbiting the sun. - Weight measures the force of gravity pulling on an object. The SI unit for weight is the Newton (N).
Vocabulary
- gravity: As traditionally defined, force of attraction between things that have mass.
Explore More
At the following URL, read about gravity and tides. Watch the animation and look closely at the diagrams. Then
answer the questions below.
http://www.mmscrusaders.com/newscirocks/tides/tideanim.htm
- What causes tides?
- Which has a greater influence on tides, the moon or the sun? Why?