1. not the “dark side” of the force
The Net Force
not the “dark side” of the force

2. The Net Force
In the expression F = ma, the a can be interpreted as the total resultant acceleration which a body receives when acted upon by some total force whose magnitude and direction are given by F.

3. Since force is a vector quantity, the total force acting upon an object is the vector sum of the separate forces that are acting. It is usually called the net force.
Where Fnet = F1 = F2 + F3 …..

4. Ex. 1 Johnny and Billy are playing tug – o – war
Ex.1 Johnny and Billy are playing tug – o – war. Each is pulling with 75 N.
Fnet = F1 + F2
Fnet = 75 + (-75)
Fnet = 0

5. Ex. 2: This time Johnny and Billy are pulling on a sled
Ex.2: This time Johnny and Billy are pulling on a sled. Each is pulling with 75 N
Fnet = F1 + F2
Fnet =
Fnet = 150 N

6. In real situations, friction is often a force that reduces the applied force (Fa)
This results in the formula Fnet = Fa +Ff
(recall that Ff like all force is a vector, so it being in the opposite direction will have a – sign associated with it.)

7. eg. Suppose a 10 kg object is being accelerated by a 10 N force
eg. Suppose a 10 kg object is being accelerated by a 10 N force. The force of friction is 6 N. What is its resultant acceleration?

8. e. g. 2 A 3 kg object is going 5 m/s at t= 0 seconds
e.g.2 A 3 kg object is going 5 m/s at t= 0 seconds. 4 seconds later it is traveling at 2 m/s. What force of friction is acting?

9. e.g. 3 A force of 50 N is applied to a snow sled at 30º above the horizontal. The force of friction present is 18 N.
Find:
Fh,
Fnet, a

11. If it started from rest, find its displacement after 4 seconds.