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

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

Calculating Force Force = (mass)(acceleration) F = ma measured in units of: kilogram-meter/second squared (kgm/s 2 )

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 Net force = 0 N

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

Unbalanced Forces 5 N 3 N 8 N 5 N ~7 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) 1)Static 2)Sliding 3)Rolling 4)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/s 2.

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.

Weight weight is the gravitational pull on an object. weight = (mass)(gravity) w = mg measured in units of: Kgm/s 2 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/s 2 )

Gravity in the Solar System Moon 1.2 m/s 2 Venus7.98 m/s 2 Jupiter31,000 m/s 2 Sun 3,244,816.1 m/s 2

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.

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

50 N 300 kg 6 m/s 2

300 kg 100 N 12 m/s 2

600 kg 100 N 6 m/s 2

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. FuelGas

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.

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

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

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