Physics Ch.2

Newton's Third Law of Motion

"If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object." for every action there is an equal but opposite reaction. if an object A exerts a force on object B, then object B will exert an equal but opposite force on object A.

static vs dynamic equilibrium

1. Objects at rest are in static equilibrium 2. Objects moving at a constant velocity are in dynamic equilibrium 3. In both cases, the net force experienced by the object must be zero Static equilibrium is when the equilibria remains posed in one position and does not move at all e.g. a balanced see-saw. In a chemical, dynamic equilibrium, change is occurring constantly. Both the forward and reverse reactions are occurring constantly but they are occurring at the same rate as each other so there is no change in the quantities of the reactants and products present.

static equilibrium

A condition where there are no net external forces acting upon a particle or rigid body and the body remains at rest or continues at a constant velocity. all acting forces always balance to zero.

equilibrium rule

For any object or system of objects in equilibrium, the sum of the forces acting equals zero. In equation form, gF = 0.

inertia

Inertia is the property of matter which mass quantifies. It describes the fact that an object at rest (not moving) will stay at rest unless an outside force acts upon it. Likewise, an object in motion will stay in motion with constant velocity unless an outside force acts upon it. Lazy ass, doesn't want to change. an object in motion tends to keep moving at a constant speed in a straight line Aristotle did not recognize the idea of inertia because he failed to imagine what motion would be like without friction.

Newton's first law of motion

Law of inertia Laziness(resistance to change) An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced/non-zero force.

Newton's Second Law of Motion

The acceleration of an object depends on the mass of the object and the amount of force applied. the amount of acceleration of a body is proportional to the acting force and inversely proportional to the mass of the body.

mechanical equilibrium

The state of an object or system of objects for which there are no changes in motion when net force on something is zero In accord with Newton's first law, if an object is at rest, the state of rest persists. If an object is moving, its motion continues without change. *is this not newtons 3rd law? The table pushes the book up( contact force) and the book pushes the table down (contact force)*

Net force

The sum of all forces acting on an object. If you both pull with equal forces in opposite directions, the net force is zero. The equal but oppositely directed forces cancel each other. One of the forces can be considered to be the negative of the other, and they add algebraically to zero, with a resulting net force of zero. it can be at rest or moving uniformly in a straight line.

scalar quantity

a quantity that can be described by magnitude only and has no direction examples: mass, volume, and speed

A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is

about 30m/s

vector quantity

any quantity that requires both magnitude and direction for a complete description examples: force velocity, acceleration

Pythagorean Theorem

a²+b²=c² or c=√a²+b²

dynamic equilibrium

consider a crate being pushed horizontally across a factory floor. If it moves at a steady speed in a straight-line path, it is in dynamic equilibrium. This tells us that more than one force acts on the crate. Another force exists - friction between crate and floor. The fact that the net force on the crate equals zero means that the force of friction must be equal and opposite to our pushing force

If no external forces act on a moving object, it will

continue to move at same speed

parallelogram

finding the resultant of two vectors that don't act in exactly the same or opposite direction, we use this rule.

Suspend your body from a pair of ropes slightly angled from the vertical and the tension in each rope will be

greater than half your weight

a force is a vector quantity because it has both

magnitude and direction

A parallelogram is a four-sided figure with opposite sides that are

parallel

Force

simplest sense, a push or pull. source may be gravitational, electrical, magnetic, or simply muscular effort.

what is tension?

stretching force

When Nellie Newton hangs at rest in the middle of a clothesline, the tension will not be the same in each side of the rope when

the angles at each side of the rope are unequal

resultant

the sum of two or more vectors

support force (normal force)

the upward force that balances the weight of an object on a surface a book on a table. The upward force must equal the weight of the book If we call the up- ward force positive, then the downward weight is negative, and the two add to zero. The net force on the book is zero. Another way to say the same thing is gF = 0.

The equilibrium rule applies to

vector quantities

vector

when the length and direction of such arrows are drawn to scale magnitude and direction

The net force acting on an insect falling downward at constant velocity is

zero

how do you calculate a perpendicular angle's resultant if each side is 1ft?

√2 x (length of one side) √2 x 1 = 1.41