Thursday, January 29, 2015 Do Now – Discuss: Do you think gravity affects surface features? Focus – What is gravity, and what factors determine the surface gravity of a planet or moon?

Surface gravity

Surface Gravity The attraction exerted by the mass of a celestial body on objects near the surface. What affects the surface gravity on different surfaces?

Explore The bottles or cans on your table represent the SAME object. The labels tell you which planet the object is on. With your group, observe how heavy the object is on each planet. Rank the object from lightest (1) to heaviest.

Observations In your notebook… Chart Planet Rank in Weight Observations Look at the data cards for each planet. Why might the weight be different on each planet?

What affects surface gravity?

Surface gravity is affected by: Mass of the objects Radius of the objects These two factors work TOGETHER to give each planet/moon a surface gravity

Newton’s Law of Gravity

Mass vs. Weight

Mass The amount of matter something has Stays constant no matter where the object is

A measure of the force of gravity on an object’s mass Weight A measure of the force of gravity on an object’s mass Since the force of gravity changes on different surfaces, weight changes depending on where the object is.

Investigate Focus Q - How are mass and weight related? Data Table Analysis compare mass and weight of each set of washers find a connection between the sets Mass Weight

Mars vs. Mercury Mars has a larger mass and a greater radius, but both planets have the same surface gravity. Mercury has a shorter radius, so objects on its surface are closer to the core, where the gravity is pulling towards.