1. TYPES OF FORCES AND FRICTION Forces

2.  A force is a push or a pull that acts on an object  A force can cause a resting object to move or it can accelerate a moving object by changing the object’s speed or direction  Example wind

3. Measuring Force The unit of force is a newton A newton causes one kilogram of mass to accelerate at a rate of 1 meter per second, each second 1N = 1 kg*m/s 2 Named after Sir Isaac Newton (much different than fig newtons)

4.  1. Adding Forces + = 2. Subtracting Forces = 3. Equal and opposite forces = 0

5. Friction Friction is a force that opposes the motion of objects that touch as they move past each other Without friction walking would be impossible, cars would slide around helplessly

6.  Static Friction is the friction force that acts on objects that are not moving  Example you are trying to push a potted plant but can not move it, static friction is working against you  Each time you step you experience static friction between the ground and your shoe

7. Sliding Friction Sliding friction is a force that opposes the direction of motion of an object as it slides over a surface It is less than static friction As the flower pot is moving there is less friction so it takes less force to move it

8. Rolling Friction The friction force that acts on rolling objects It is about 100 to 1000 times less than static or sliding friction Example ball bearings used to reduce friction in machines

9. Fluid Friction The forces that opposes the motion of an object through a fluid You would feel this friction when you are stirring cake batter Fluid friction increases as the speed of the object increases

10. Fluid Friction cont. Fluid friction acting on an object through the air is known as air resistance Bicyclists and speed skaters will wear slick racing suits to reduce air resistance