AP Physics 1 - Chapter 2

Both the center of mass of an object and the center of mass of a system obey…

Newton’s Laws

terminal velocity

constant velocity reached when all forces balance out

ideal string

negligible mass, doesn’t stretch, tension is the same at all points

ideal pulley

negligible mass and friction, rotates about an axle that goes through its center of mass

In what reference frame can an observer verify Newton’s 1st Law?

an inertial reference frame (not accelerating)

translational equilibrium

configuration of forces so the net force = 0 N

equivalence principle

observer in a noninertial reference frame can’t tell apparent weight from actual weight

What does a scale read, and what does it not read?

reads the force of the scale on the object, not the object’s actual weight

Difference between F_g and g?

F_g = weight, g = strength of gravitational field (acceleration)

What does r represent in Newton’s Law of Universal Gravitation?

the distance between the 2 objects’ centers of mass; not always the radius (of the planet)!

Equation for finding the gravitational constant of any planet

g = (G*m_planet) / r²

m/s/s =

N/kg

How do you calculate the factor of change when you are given actual numbers? What do you do at the end of the problem?

new/original; at the end, multiply the overall factor of change by the original value that is changing

What does apparent weight depend on?

how much normal force is exerted on the object

When does an object appear to be weightless?

either:

1. No forces are exerted on it (actually weightless)

2. F_g is the only force exerted on it (it’s in free fall)

In which equation can the type of mass differ?

N2L: a = ∑F / m

• any mass in ∑F is gravitational mass

• m in denominator is inertial mass

When can an object accelerate due to static friction?

• it’s rolling

• the surface it’s on is accelerating

What does the coefficient of friction depend/not depend on?

• depends on 1) types of surfaces and 2) how much they’re touching (amount of normal force)

• doesn’t depend on velocity or surface area

ideal spring

negligible mass, exerts force (directed toward equilibrium position) proportional to change in length, reforms

• has limit of proportionality

What is k in?

N/m

tangential velocity

v = 2πr / T

centripetal force

F_c = mv² / r

What is tangential acceleration?

the rate at which the magnitude of the tangential velocity changes

What is the net acceleration in circular motion?

the vector sum of centripetal acceleration and tangential acceleration; not always toward the center like the net force is

Parallel and perpendicular net force in circular motion

• parallel ∑F: ma_t

• perpendicular ∑F: ma_c

equation for tangential velocity of something orbiting a planet

v = sqrt(Gm_planet / r)

Kepler’s 3rd Law

T² = (4π² / Gm_planet) * r³

• calculates time for 1 revolution - if orbiting the sun, 1 year

What happens at the top of a vertical circle of circular motion?

a minimum speed is needed; at this minimum speed, a_c = F_g

• v = sqrt(gr)

What causes the centripetal acceleration on a bank?

components of the static friction force and the normal force

T in relation to frequency

T = 1/f