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

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.

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 …..

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

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 =75 + 75 Fnet = 150 N

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.)

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?

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?

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

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