1. Bell Work
A bag of baseballs is suspended motionless from the ceiling by two ropes. Draw the Free Body Diagram of the bag and label all the forces
A pebble is free-falling from the roof of a tall building. The wind is blowing westward. If there is air resistance, draw the possible scenario in a Free Body Diagram.

2. Forces Part 2: Laws of Motion
Seo
Physics

3. Net Force What is a Net Force? Σ = Sigma
Total or Overall Forces in the object
Fnet = F1 + F2 + F3 + …..
Σ = Sigma
ΣF mean the sum of or Net force
If equal = BALANCED
If NOT equal = UNBALANCED

4. Net Force Practice 1 Top - Bottom Upward Force of 50 N
Downward Force of 50 N
Net Force is
Fnet = Top Force – Bottom Force
Fnet= 50 N – 50 N
Fnet = 0 N
OR ΣF= 0 N
Top and Bottom are Equal
BALANCED

5. DIY 1 Top - Bottom Upward Force of 80 N Downward Force of 20 N
Net Force is
Fnet = Top Force – Bottom Force
Fnet= 80 N – 20 N
Fnet = 60 N
OR ΣF= 60 N
Top Force is greater than the Bottom Force
UNBALANCED

6. Net Force Practice 2 Right - Left Rightward Force of 30 N
Leftward Force of 30 N
Net Force is
Fnet = Right Force – Left Force
Fnet= 30 N – 30 N
Fnet = 0 N
OR ΣF= 0 N
Right and Left are Equal
BALANCED

7. DIY 2 Right - Left Rightward Force of 30 N Leftward Force of 80 N
Net Force is
Fnet = Right Force – Left Force
Fnet= 30 N – 80 N
Fnet = -50 N
OR ΣF= -50 N
Left Force is greater than the Right Force
UNBALANCED

8. Newton’s Three Laws of Motion

9. 1st Law of Motion (Inertia)
What is Inertia?
Object’s resistance to move
What is the 1st Law?
An object at rest will stay at rest
An object in motion will stay in motion,
unless acted upon by an outside force
EX). Your notebook is not going to move unless you push it

10. 2nd Law What is the 2nd Law? Units?
Force is equal to mass multiplied by acceleration
Equation?
F = m*a (Force = mass * acceleration)
Units?
(N) = (kg) * (m/s2)

11. 2nd Law Practice
How much force is needed to accelerate a kilogram car 3 m/s2?

12. DIY
1. What acceleration will result when a 12 N net force applied to a 3 kg object?
SOLN: 12 N = 3 kg x a a= 4 m/s2
2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass.
SOLN: 16 N =m x 5 m/s2 m= 3.2 kg
3. How much force is needed to accelerate a 66 kg skier 1 m/s2?
ANS: 66 kg*m/s2 or 66 N
4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/s2?
ANS: -9800 kg*m/s2 or 9800 N downward direction

13. 3rd Law
What is the 3rd Law?
For every action, there is an equal and opposite reaction Force
EX). If I push the wall with a Force, the wall will push me back with an equal Force

14. Net Forces w/ 2nd Law Practice
Fnet= m*anet OR ΣF= m* a
a=9.8 m/s2 , unless given a different value
EX). Find the mass of the hanging object
(Ftension- Fg)=m*a
(80 N-30 N)=m*a
(50 N)= m*(9.8 m/s2)
m= (50N)/(9.8 m/s2)
m= 5.10 kg

15. DIY
Smiley is rolling at an acceleration of 5 m/s If it has a mass of 2 kg, find the Force of push
Fnet= m*anet OR ΣF= m* a
(Fpush- Ffr)=m*a
(Fpush - 80N)=(2 kg)*(5 m/s2)
(Fpush – 80N)= 10 kg*m/s2
(Fpush – 80N)= 10 N
Fpush =90 N \

16. 2nd Law – Force equals mass times acceleration (F= m*a)
Summary
1st Law – An object at rest will stay at rest, and an object in motion unless acted upon by an unbalanced force.
2nd Law – Force equals mass times acceleration (F= m*a)
3rd Law – For every action there is an equal and opposite reaction Force