Section 1: The Nature of Force Force – a push or pull on an object; causes an object to accelerate. 3 m/s 0 m/s

F = ma Calculating Force Force = (mass)(acceleration) measured in units of: kilogram-meter/second squared (kgm/s2)

kilogram-meter/second squared a.k.a. Newton (N)

Two Types of Forces balanced forces – forces of equal strength & acting in opposite directions; net force always equals zero Newtons. 5 N 5 N Net force = 0 N

unbalanced forces – forces of unequal strength &/or act in different directions; causes an object to move. 2 N 5 N Net force = 3 N 3 N

Unbalanced Forces 5 N 8 N 3 N ~7 N 5 N 5 N

Section 2: Friction & Gravity friction- the force that two surfaces exert on each other when they rub against each other. 4 Types of Friction: (strongest to weakest) Static Sliding Rolling Fluid - air resistance is the most common form.

gravity – a force that pulls objects toward each other. Gravity causes objects to accelerate toward earth at: 9.8 m/s2.

Gravity also causes:

Law of Universal Gravitation states that due to gravity every object in the universe is attracted to every other object in the universe.

w = mg Weight weight is the gravitational pull on an object. weight = (mass)(gravity) w = mg measured in units of: Kgm/s2 a.k.a. Newtons

Calculate your REAL weight Step 1) Find your mass: # of lbs / 2.2 = # of kgs. Step 2) Calculate your weight w = (# of kgs.)(9.8 m/s2)

Gravity in the Solar System Moon 1.2 m/s2 Venus 7.98 m/s2 Jupiter 31,000 m/s2 Sun 3,244,816.1 m/s2

Newton’s First Law (Law of Inertia) An object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity, unless an unbalanced force acts upon it.

inertia – the tendency of an object to resist changes in its motion.

F = ma Newton’s Second Law force, mass and acceleration are related with the formula: F = ma

50 N 6 m/s2 300 kg

12 m/s2 100 N 300 kg

6 m/s2 100 N 600 kg

Newton’s Third Law if one object exerts a force on another object, then the second object will exert a force of equal strength in the opposite direction back on the first object. Fuel Gas

momentum – the product of an object’s mass and velocity. momentum = (mass)(velocity) p = mv measured in units of: kilogram-meter/second

Law of Conservation of Momentum states that: the total momentum of a group of objects remains constant in other words: the total momentum of objects before a collision equals the total momentum after a collision.

Before the collision 0.3 kg 0.25 kg C 1.5 m/s 0 m/s p = 0 kgm/s 8 C 1.5 m/s 0 m/s p = (0.25 kg)(1.5 m/s) p = (0.3 kg)(0 m/s) p = 0 kgm/s p = .38 kgm/s pt = .38 kgm/s + 0 kgm/s pt = 0.38 kgm/s

After the collision 0.3 kg 0.25 kg C 0.75 m/s 0.63 m/s p = 0.19 kgm/s 8 0.75 m/s 0.63 m/s p = (0.25 kg)(0.75 m/s) p = (0.3 kg)(0.63 m/s) p = 0.19 kgm/s p = 0.19 kgm/s pt = 0.19 kgm/s + 0.19 kgm/s pt = 0.38 kgm/s