TO GRAVITY

Name __________________________________________________ Date ___________ Period _____ H:\My Doc's\Physics Crymes\Physics Labs\Acceleration due to Gravity.doc The rate of change in velocity of an object as it falls is known as the acceleration due to gravity (g). The value of g on Earth varies slightly with altitude, but you may use -9.8m/s² as an estimate for g. This means that if you drop an object (while at the same time waving a magic wand to eliminate air resistance) the object's velocity will increase -9.8m/s every second. For example: An object will be traveling -9.8m/s after 1s, -19.6m/s after 2s, -29.6m/s after 3s and so on. In this experiment you will drop several different objects and calculate their acceleration.

S

The target.

Purpose

To calculate the acceleration due to gravity.

To identify factors that effect results.

Procedure

1. Station your group at the top of the bleachers.

2. Set up the timing apparatus according to your teacher's instructions.

3. Drop the object.

4. Record the time of free fall in the data table.

5. Repeat steps 2 - 4 with nine other objects.

6. Make sure all objects from all students have landed before continuing to step 7.

7. Measure and record the free fall distance(s) in meters. Make sure you follow your teacher's instructions for making measurements.

By the way, you may notice that all of a sudden, the variable for distance in this lab is denoted by an 's'. Ask your teacher why.

Materials

10 different objects to drop

Timing apparatus

Tape measure or meter stick and string

Safety

Do not sit or stand on ledges.

Stay out of the target area until all

the objects have been dropped.

Use common sense.

Make sure you know where a

dropped object will land.

Name __________________________________________________ Date ___________ Period _____ H:\My Doc's\Physics Crymes\Physics Labs\Acceleration due to Gravity.doc Data and Calculations

Data table Calculations table

Trial #	Object name	times [sec]	Average time [sec]	g [m/s2]
1
2
3
4
5
6
7
8
9
10

1. Which object or (if it was a tie) objects encountered the most air resistance?

   __________________________________________________________________________

1. How can you tell which object encountered the most air resistance?

   ____________________________________________________________

2. Calculate the acceleration due to gravity for each trial and record your answers in the calculations table. Use the formula below. You must work one sample problem completely and perfectly so that someone reading you research paper can see exactly what you did. Remember to show all of your work, your units, your steps, and your beginning values.

   s = gt²

3. Name one factor (NOT including human error) that may have affected the accuracy of the

   results: ______________________________________________________________________

   ____________________________________________________________________________

4. Ok, now EXPLAIN two sources of human error: _____________________________________

   ____________________________________________________________________________

   ____________________________________________________________________________

   Application and Critical Thinking

5. Let's say someone drops two watermelons off a skyscraper. The second watermelon is released 1s after the first watermelon. Will the vertical distance between the melons always be the same?

   ____________ (Warning: Do not try this experiment. This is a thought experiment.) Explain.

   ___________________________________________________________________________

   ___________________________________________________________________________

   ___________________________________________________________________________

   ___________________________________________________________________________

6. In question 6, what will the difference in velocity between the melons be after 4 s of free fall? (You can figure out the answer with equations or answer with an explanation)

7. What will it be after 5 seconds? __________ What will it be after 6 seconds? ____________

8. So, if one object is dropped and then another object is dropped, the distance between the objects

   will circle oneÞ (increase / decrease / remain the same) as they fall and the difference between

   their velocities will circle oneÞ (increase / decrease / remain the same).

9. Problem: The acceleration due to gravity on a neutron star is about 1 *10¹¹m/s². What distance

   would a small object travel if it fell for 0.0001 s on a neutron star? Write the complete mathematical solution below.

10. Problem: On Mimas, a moon of Saturn, the acceleration due to gravity is 0.066 m/s². Starting

    from rest, how much time does it take for an object to fall 10 m on Mimas? Write the complete mathematical solution below.

11. Suppose you throw a baseball straight up. Compare the time for the ball to rise (t_up) with the time

    it takes for the ball to fall (t_down). Which time is longer if there's no air resistance? ____________

    Which time is longer if there is air resistance? ________________

    Explain why these are different: ___________________________________________________

    _____________________________________________________________________________

    _____________________________________________________________________________