Gravity and
free fall
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community
Ask the community for help and clear up your study doubts
University Rankings
Discover the best universities in your country according to Docsity users
Free resources
Our save-the-student-ebooks!
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
A falling human has a terminal velocity of about 140 miles per hour (or about 60 m/s).
Typology: Exams
2021/2022
1 / 32
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download Gravity and free fall and more Exams Physics in PDF only on Docsity!
Gravity and
free fall
Physics terms
- acceleration
- free fall
- gravity
An object is in free fall whenever it moves solely under the influence of gravity, regardless of its direction.
A ball falling down, with negligible air resistance
What is free fall?
A ball thrown up, with negligible air resistance
A ball launched at ANY angle, as long as there is negligible air resistance
The only difference is that you already know the acceleration because it is always 9.8 m/s 2 downward.
The free fall equations are identical to the equations for motion with constant acceleration:
Describe free fall with equations
Acceleration is always equal to -9.8 m/s 2 in free fall
If an object is dropped from rest then...
- after 1 second its velocity is -10 m/s.
- after 2 seconds its velocity is -20 m/s.
- after 3 seconds its velocity is -30 m/s
- after 4 seconds its velocity is -40 m/s. .... and so on....
REALLY?
Do falling objects REALLY keep moving faster and faster?
Gravity and free fall
Do falling objects REALLY keep moving faster and faster?
No! In real life there is air resistance.
As falling objects speed up, the force of air resistance increases.
When the air resistance gets as strong as the force of gravity, the falling object stops accelerating.
Gravity and free fall
Parachutes increase air resistance.
Opening a parachute changes the terminal velocity from a fast, deadly speed to a low, safe speed.
Terminal velocity
When did the parachute open?
A skydiving trip
A skydiving trip
What is happening to the acceleration during each of these time segments?
Free fall is NOT a good approximation for light objects, or an object with a large surface area compared to its weight (like a parachute).
When can motion be
treated as free fall?
Free fall is a very good approximation for solid, dense objects dropped from ten meters or so.
For these situations, air resistance can be ignored.
The symbol g is often used when the acceleration
of an object is due only to gravity.
When can motion be
treated as free fall?
- Define your coordinate system:
- If you decide up is positive, g = -9.8 m/s 2
- If you decide down is positive, g = +9.8 m/s 2
2) Write the equations of motion, substituting g for a.
Eliminate any terms that are zero.
Work out a solution strategy.
Solving free fall problems
Example free fall problem
From what height should you drop a ball if you want it to hit the ground in exactly 1.0 second?
Asked: x
Given: t = 1.0 s, g = -9.8 m/s 2
(assume v 0 = 0 m/s and x 0 = 0 m)
Equation:
Solve:
Example free fall problem
From what height should you drop a ball if you want it to hit the ground in exactly 1.0 second?
Asked: x
Given: t = 1.0 s, g = -9.8 m/s 2
(assume v 0 = 0 m/s and x 0 = 0 m)
Equation:
Solve: