How do we measure force? The unit used to measure force is the Newton (N)
Direction of the force The direction of a force is the direction of the push or pull. In what direction is the push or pull below?
Combining Forces When more than one force acts on an object, the forces combine. The combination of all the forces on an object is called the net force.
How do forces in the same direction combine? ADD the forces together to form net force. What is the net force below? 10 N
How do forces in opposite direction combine? SUBTRACT: larger force minus the smaller force What is the net force below? In what direction will the object move? Larger force - smaller force 6 N - 3 N = 3 N To the left 3 N
What is inertia? The tendency of an object to resist a change in its motion. Mythbusters: Tablecloth Inertia
The more mass an object has, the greater its inertia. Which is harder to push??
Wear seat belts! Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 km/hour. Don’t let this be YOU!
Contact Force A force exerted only when two objects are touching each other. Friction Air Resistance Buoyant force Tension Compression Non-contact Force A force exerted by one object on another object when the objects are not Touching Gravity Electrical force Magnetic force
Friction A force that opposes the motion of two surfaces in contact. Smoother surfaces = less friction Rougher surface = more friction