Post on 09-Feb-2016
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FORCE & FRICTION
Force: push or pull all forces have size and direction measured in Newtons (N)
Science Pushes and Pulls, but it
NEVER Sucks!
An object willspeed up,
slow down,or turn
Only if something is pushing or pulling on it.
Usually, more than one force is acting on an object.
Net Force: Combination of all forces on an object
Determines motion of object (similar to total velocity)
Combining Forces
Forces in the Same Direction
When forces act in the same direction, you add the forces to determine the net force. The net force will be in the
same direction as the individual forces.
25 N20 N
Net Force25 N + 20 N = 45 N to the right
Forces in Different Directions
When two forces act in opposite directions,subtract the smaller force from the larger force. The net force will be in the same direction as the larger force.
35 N
20 N
Net Force35 N – 20 N = 15 N Up
Balanced and Unbalanced Forces
This is ZERO fun!!!
Balanced Force: Net Force = ZERONo CHANGE IN MOTION
12 N 12 N
Balanced and Unbalanced Forces
Unbalanced Force: Net Force = NOT zero CHANGE IN MOTION
Eat it!!!
Don’t wipe that on
me!
12 N
20 N
BEWARE OF THESE FORCES!
What force was missing in the video?
Friction: slows motion, can cause moving objects to slow down and stop
FRICTION—What a Drag!As force increases, friction increases.
The rougher the surface is, the greater the friction is.
Kinetic Friction: “moving”, friction between moving surfaces
Rolling and Sliding FrictionUnbalanced Force—Net Force Doesn’t = Zero
Static Friction: “not moving”Balanced Force—Net Force = ZERO
Types of Friction