Free Fall
Motion Under the Influence of Gravity
Freefall
Free Fallin'Tom Petty
What did Galileo teach the world about falling bodies?
Galileo (1564 - 1642)
Credit: Original portrait by Justus Sustermans painted in 1636.
Questions to Ponder
1. Describe the motion of a falling body.
2. What are the forces affecting the motion of a falling body?
3. In the absence of air friction, how would the acceleration of a large mass compare with the acceleration of a small mass?
Free Fallin'
Video Instruction
showmethephysics.com
I. Motion of objects moving freely under the force of gravity.
Freefall - falling where the only force is gravity
“Do the examples below show freefall?”
Galileo (1564 - 1642)
Credit: Original portrait by Justus Sustermans painted in 1636.
[Flash]
Rutgers U.
Click on the Arrow
Free Fall
D vs. t Plot
Rutgers U.
Distance and Time
Rutgers U.
(Roll your mouse over this)
[Flash]
Show Me The Physics
Gravity/Moon
Feather & Hammer
NASA
showmethphysics.com
Meet Galileo Galilei — the physicist behind this discovery
Ex) An Object Thrown Upward at +40 m/s
Show Me The Physics
An object is thrown up at a velocity of 30 m/s.
About how long will it take to hit the ground?
| V (m/s) | Time (sec) |
|---|---|
| 30 | 0 |
| 20 | 1 |
| 10 | 2 |
| 0 | 3 |
| -10 | 4 |
| -20 | 5 |
| -30 | 6 |
A. Motion Diagram for Free Fall
On any planet or moon
Acceleration due to gravity is CONSTANT near the surface of any planet or moon.
Label the slope pictured above that could be Jupiter? Moon?
D vs t - Free Fall
A ball is thrown upward.
What's the acceleration due to gravity at the peak?
AP Question
Compare the displacement of an object dropped during its first second with its displacement after 3 seconds.
Δd = Vit + ½aΔt2
Δd = ½aΔt2
NYSSLS Reading Passage · 1D Motion
The Physics of the Plunge: Force, Acceleration, and Terminal Velocity
Open Reading Passage → Regents Practice Version →Check Your Understanding
5 quick questions — pick an answer to see if you’re right.
1. What is freefall?
2. Ignoring air resistance, a heavy ball and a light ball are dropped together. How do their accelerations compare?
3. Using g ≈ −10 m/s², about how long does a ball thrown straight up at 30 m/s take to return to the thrower's hand?
4. A ball is thrown straight upward. What is its acceleration at the very top of its path?
5. An object is dropped from rest. How does its displacement after 3 s compare with its displacement after 1 s?
Measuring Reaction Time With a Falling Ruler
Students measured their reaction times. One student holds a meter stick vertically; a partner holds her fingers open at the 0-cm mark. Without warning, the stick is released and the partner catches it as quickly as possible. The distance the stick falls before being caught is used to find reaction time. Air resistance is negligible.
Table 1: Catch Distances
| Student | Distance Fallen (m) |
|---|---|
| Jordan | 0.20 |
| Priya | 0.15 |
| Malik | 0.30 |
What was Jordan’s reaction time?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. Which student had the fastest reaction time?
C2. Substitute numerical values into a mathematical representation that can be used to determine Priya’s reaction time. Then calculate her reaction time.
C3. A student makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.
C4. Which graph best represents the stick’s speed versus time as it falls?
C5. Determine the speed of the meter stick at the instant Malik catches it.
C6. The students want to print a scale on the meter stick that reads reaction time directly. Explain why marks for equal time intervals (0.05 s, 0.10 s, 0.15 s, 0.20 s) would not be equally spaced along the stick, and describe how the spacing changes.
