1. Free Fall
October 21, 2015

2. Bell Work

3. Agenda Quiz Read pages 37-48 Review Questions 4-20 pages 49-50
Finish Lab (1st hour only)
Notes
Finish Questions for homework

4. Goals
Define Free Fall

5. Q: If an apple falls from a tree, why does it accelerate?
A falling object is affected by the pull of gravity
We say the object is in “free fall” when only gravity is acting on it

6. Q: If an apple falls from a tree, why does it accelerate?
Gravity is an unbalanced force acting on the object, causing the object to change it’s velocity
Remember: If all forces are balanced (net force of 0 N) the object will not change speed or direction!

7. Q: If an apple falls from a tree, why does it accelerate?
On Earth, the acceleration due to gravity (symbol g) is 9.8 m/s2

8. Q: We know Newton’s 1st Law (object in motion remains so at same speed and direction), so what is Newton’s 2nd Law?
States: the unbalanced force acting on an object (to move it) equals the object’s mass times its acceleration
Tells us how the unbalanced force will affect the movement of an object

9. Newton’s 2nd Law Formula: F = ma
UNITS: before you can calculate you must have numbers with these units!
F = Force in Newtons (N)
m = mass in kilograms (kg)
a = acceleration in m/s2 F m a

10. Newton’s 2nd Law
The second law shows that acceleration and mass are inversely proportional to each other
Inversely proportional means that if one value increases the other value will decrease, assuming everything else stays the same.

11. Practice Problem: A baseball accelerates downward at 9. 8 m/s2
Practice Problem: A baseball accelerates downward at 9.8 m/s2. If the gravitational force acting on the ball is 1.4 N, what is the mass of the ball?
What are we given?
Formula
Work?

12. Newton’s 2nd Law Let’s take a look at the units… Kg*m s2
1 N = 1 kg*m/s2
A NEWTON is defined as the amount of force needed to move a 1 kg mass object at an acceleration of 1 m/s2
Kg*m s2 m