1.  Place a meter stick across two desks so that it spans the gaps between the desk.

2.  Rest a book on top of the meter stick.  Using another ruler, measure how much the meter stick sags under the book's weight.

3.  Place another book on top of the first book.  Measure how much the meter stick sags under the weight of two books.

Observing:
Did the meter stick sag more with two books resting on it?
Why?
Why doesn't the meter stick break?
 
 

Spinning Plates
You can compare rolling friction to sliding friction.

1.  Stack two ientical pie plates together.  Try to spin the top plate.

2.  Now separate the plates and fill the bottom of one o]pie plate loosely iwth marbles.

3.  Tryp to spin the top plate again.  Observe the results.

Drawing Conclusion:
How does sliding friction compare to rolling friction?
How do you know?
Is it posslbe to get the top plate to spin forever? Explain.
 

Gravity

Demonstration
    Dropping a ball and dropping a piece of paper.
    Dropping the same ball and dropping the same piece of paper crumbled up.
        Which will hit the ground first?

As you watch the video, listen to the information given by the astronauts.

1.  Who first claim that all things fall at the same rate?

2.  What objects were used to prove the claim that all objects fall at the same rate?

3.  Why can't we use the same objects on earth to show the same event?
 
 

Measuring Mass and Weight

Materials:  spring scale, triple -beam balance

Define mass:
Define Weight:
 

1. Which instrument is used to measure mass?
    What is the unit of measurement?

2.  Which instrument s used to measure weight?
    What is the unit of measurement?

3.  If we went to the moon and set up this same activity, which instrument would measure the same, and, which would measure a different amount?

4.  What is measured by a bathroom scale?
 
 

Calculating

You can determine the weight of an object if you measure its mass.

Use the following formula for finding the weight.

      Weight(N)  =  mass(g)  X  gravity(m/s²)             Earth's gravity 9.8m/s/s (9.8m/s²)
                                                                                      Moon's gravity 1.6 m/s/s(1.6m/s²)

1,  Use the triple  beam balance to find the mass of each object.
      Convert to kilograms.
        (use dimensional analysis -  given measurement X conversion factor = desired measurement)

 
2.  Calculate the weight (N) for the earth and the moon using the formula and given gravities for each  object.

3.  The unit for weight is the same for force because weight is a special force.
                Force = mass X acceleration      Weight = mass X gravity