# IB1 Physics Ch. 6-7

## 18 terms · Yeah.

### Momentum

A vector quantity defined as the product of an object's mass and velocity. (p=mv)

### Impulse

The change in the momentum of an object.

### Impulse-Momentum Theorem

FΔt = m(vf - vi)
Assuming constant mass.

### Conservation of Momentum

In a closed, isolated system (no net external forces), the total momentum of the system must remain constant.
Total Momentum before = Total Momentum After
(p1i + p2i) = (p1f + p2f)

### Elastic Collision

Two objects collide and bounce off of one another with NO mechanical energy lost (no kinetic energy lost; they "cancel out" like a bouncing ball)
Momentum is still conserved.

### Inelastic Collision

Two objects collide and bounce off of one another or stick together, but there IS mechanical energy lost in the process ("absorbed" like a piece of gum sticking to the wall after being thrown)
Momentum is still conserved.

### Centripetal Acceleration

Acceleration of an object moving in a circle (no constant velocity because its direction is always changing; therefore, it is accelerating). Always points towards the center of the circle.
a = v² / r

### Centripetal Force

According to newton's Second Law, if there is an acceleration, then there must be a force; this is whatever force is pointing towards the center of the circle (setup coordinate system so that one of the axis points towards the center of the circle).
F = ma = mv² / r

### Newton's Law of Universal Gravitation

The force of gravity that acts on objects here on earth is the same as the force keeping planets moving in orbit.
F = G(m₁m₂) / r² where G = 6.673 x 10⁻¹¹ Nm²kg⁻²

### Gravitational Field Strength

The gravitational force exerted per unit mass at a particular point in the gravitational field.
g = G(M) / r²

### Gravitational Potential Energy

Defining some point as zero potential energy, calculating potential energy as normal.
ΔPE = -G(Mm) / r

### Gravitational Potential

The gravitational potential energy per unit mass in a gravitational field.
ΔV = -G(M) / r

Telling us that the gravitational field always points in the direction of decreasing gravitational potential. Objects in a gravitational field will always naturally move towards a lower energy position.
g = -ΔV / Δx

### Escape Velocity

The minimum speed necessary to launch an object in order to give it enough kinetic energy to break free of Earth's gravitational pull.
v = ( 2GM / r )^½

### Kinetic Energy of an Orbiting Satellite

The force that holds an object in circular orbit around the Earth's gravity.
Velocity: √(GM / r)
Kinetic Energy: GMm / 2r

### Period of an Orbiting Satellite

How long it takes to orbit an object once.
T = √( 4π²r³ / GM )

### Kepler's Third Law

(T1/T2)² = (r1/r2)³

### Energy Considerations in Satellite Motion

Ab orbiting satellite has both gravitational potential energy, as well as kinetic energy.
-GMm / 2r