2.  How would you describe “friction” to someone who didn’t know that word?  What do you think the word “Force” means?

3.  NOTES: Forces & Newton’s Laws What is force? Net Force 5 types of Forces Newton’s Laws of Motion

4.  A force is a push or a pull that causes an object to change its motion.  Forces can cause objects to accelerate: Slow Down Speed Up Change Direction

5.  The unit used to measure force is the Newton (N). One Newton is to equal to the force that would give a mass of 1 kg an acceleration of 1 m/s each second.

6.  Net force is the overall force acting on an object. Think about what the word “net” means (not like a fishing net). How can this help you remember what a net force is?  Forces can be represented by arrows since they are vectors.

7.  A force diagram shows all of the forces acting on an object.

8.  When forces are balanced they have a net force of zero. No change in movement. Net Force = 0 N

9.  When forces are unbalanced the net force is not zero. Causes movement Net Force = 5 N to the right

12.  5 Types of Forces to Know: Friction Gravity Normal Applied Tension

13.  FRICTION is a force that opposes sliding between two surfaces.  The friction force on an object always points in a direction opposite to the relative motion of the object. Brakes push against the wheels of a car or a match rubs against a strikepad.

14.  GRAVITY pulls objects towards one another. Airplanes are pulled towards the ground and our planet is pulled towards the sun.

15.  Gravity is what causes objects to have weight.  Mass is the amount of matter in an object.  Weight is the force of gravity acting on an object so it is actually a measure of force.

16.  The NORMAL FORCE is a push directed at right angles from the surfaces of the interacting objects. The ground pushes up against our feet.

17.  APPLIED FORCES are when one object pushes another. A batter pushes a baseball with his bat.

18.  Tension force occurs when a non-slack rope, wire, cord or similar device pulls on another object. A string holds up a kilogram weight or a girl hangs from trapeze rings.

19.  In the 1600’s, Isaac Newton invented 3 laws that describe how and why things move.  The 3 Laws: Law of Inertia Law for Calculating Forces (F=ma) Law of Action and Reaction

20.  An object at rest will stay at rest and an object in motion will stay in motion unless it is acted upon by an unbalanced force.  Objects only change their speed or direction when a force makes them.  This tendency to resist change is called INERTIA.

21.  Force = (mass)(acceleration) More force causes more acceleration. More mass causes less acceleration. The heavier something is (more mass), the more force it takes to change its speed or direction.

22. 1 st video clip: Willis McGahee 230 lbs https://www.youtube.com/watch?v=8qNj6j UcPN8 2 nd video clip: Brandon Jacobs 270 lbs https://www.youtube.com/watch?v=1r3yu Wcd6zk Both running back will be hit by a safety while running full speed. Watch the difference.

24. A car with a mass of 1200 kg accelerates at a rate of 3 m/s 2. What is the net force acting on the car? F = ma F = (1200 kg)(3 m/s 2 ) F = 3600 N

25.  What is the acceleration of a 1200 kg car acted upon by a net force of 250 N? a = F/m a = 250 N / 1200 kg a = 0.21 m/s 2

26.  Remember weight is the force due to gravity.  Knowing this concept we are able to calculate weight using the acceleration due to gravity on Earth. What is the acceleration due to gravity on Earth?  9.8 m/s 2  Ex. Calculate the weight of a person on Earth with a mass of 520 kg. W = ma = (58 kg)(9.8 m/s 2 ) = 568.4 N

27.  For every action, there is an equal and opposite reaction.  In other words, whenever something gets pushed, it pushes back.

28.  Newton’s Laws and Forces Worksheet