The Invisible Force of Gravity

By Emily Weil

9/10/09

Science Standard 3- The Physical Setting

• Indicator 5.3.6- Demonstrate that things on or near Earth are pulled towards it by Earth’s gravity.

• Taken from: http://www.indianastandards.org/standardSummary.asp?Subject=sci&Grade=5.

• Link to Activity: http://www.indianastandards.org/files/sci/sci_5_3_pull.pdf.

Definitions

• Gravity- Force of attraction that causes objects on Earth to fall towards the center (or downward).

• Force-Push or Pull on an Object.

• Balancing Point (Center of Gravity)- Point of an object that is closest to the ground (where weight equal on all sides).

• Weight-

• Mass- Amount of matter in an object.

Testing Gravity

• The mass of an object determines its gravity.

• Weight has a direct relationship with gravity (mass is not the same thing as weight)

– An object of the same mass can have different weights when there are different gravities

• Gravity can vary from place to place (the moon and other planets all have different gravities).

– Your weight (you keep the same mass) is different on Earth than it is on the moon.

Try it out!

• Look at the given chart and equations:– Pluto- weight/7.5– Mercury- weight/2.9– Mars- weight/2.63

• Calculate your weight using the equations.• What happens? Is your weight greater with greater

force of gravity?• Now let’s test whether gravity affects the speed of

descent. – Use to two objects (weight them) given and drop them

from the same height• Do they fall at different speeds?