HMWK tonight (102/103) Today in class: Demonstration of shooting a monkey/bear, depending on the class :-) showing, once again, that gravity does not affect horizontal motion of an object, and that projectiles (things moving through the air) curve due to this effect.
Notes: Inertia and Newton's 2nd law (below)
Announcement: If you need a book (a real book), Seckman has given FHS back some of our texts they borrowed in the past. See Mr. F. for a text to check out.
Notes:
Newton's 1st Law (Inertia): An object in motion remains in motion, an object at rest remains at rest... UNTIL/UNLESS acted upon by a net force.
Definition: Inertia is: Resistance to Acceleration
remember, acceleration is any change in velocity, which may be resulting from a change in speed OR direction.
Inertia is based on mass. More mass --> more inertia!
Newton's 2nd law: An object's acceleration depends on 2 things: Net force acting on it AND its mass.
This one has an equation: Fnet = m * a (net force = mass * acceleration)
Units: mass (kg) acceleration (m/s^2) and force is (kg*m/s^2) or just N (Newton). (Newtons are a derived unit - short for kg*m/s^2)
Practice problem:
5N net force
2 kg mass
a = ?
How to solve: Fnet = m*a <-- divide both sides of this equation by "m" to get: Fnet/m = a.
Put in numbers and you get 5N / 2kg = a Simplify to 2.5 N/kg.
**But you say N/kg isn't acceleration? Sure it is! Substitute kg*m/s^2 in for N in the above answer, and you should see that kg are in the numerator and denominator; they cancel, leaving 2.5 m/s^2.
Some classes also asked questions and had answers worked out for tonight's homework.
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