REGENTS PHYSICS STAMPS

In freefall acceleration is always

constant (-9.8 m/s²) near the Earth's surface.

Friction / (air resistance)

the resistance that one surface or object encounters when in motion

In freefall when an object reaches it maximum height

The finalpoint at which the object's velocity becomes zero before descending due to gravity.

Scalar

A physical quantity that has only magnitude and no direction, such as mass or temperature. * cant be negative

Vector

A physical quantity that has both magnitude and direction, such as force or velocity. *can be negative

When an object moves downward in projectile motion

Acceleration is positive as gravity is helping the object increase it’s speed as it falls.

Projectile Motion

An object moves along a curved path under the influence of gravity and has both horizontal and vertical components of motion.

In projectile motion when an object is thrown downward, it’s vertical velocity

Increase in the negative direction because it going down the y-axis

• Gravity is constantly accelerating the rock in the y-direction.

In projectile motion the horizontal velocity

is constant if air resistance is neglected

When the angle in projectile motion increases

The total horizontal distance of the projectile traveled increases & maximum altitude also increases.

Newtons 1st Law

An object in motion will stay in motion and an object at rest will remain at rest unless acted upon by unbalanced a force.

Newtons 2nd Law

Fnet = m x a

• When a force acts on a object without friction / air resistance object begins to accelerate towards the direction in which the force of motion moves (usually to the right).

Inertia

An objects tendency to resist change depending on mass

Greater mass = Greater inertia

objects with heavier mass have a higher tendency to resist change

Equilibrium

When balanced forces are acting on an object causing it to stay still or move at a constant velocity

What causes an object in motion to stop moving

When an unbalanced force acts upon it

What causes an object at rest to begin moving

When an unbalanced force acts upon it

When an object is at rest in equilibrium

Fnet = 0 N

V = 0 m/s

A = 0 m/s2

When an object moves at constant velocity at equilibrium

Fnet = 0N

a = 0 m/s2 → No change in magnitude of velocity = 0 acceleration

How does frictional force move?

It works against the force of motion making it harder to move things

Kinetic Force

Is a resistive force → meaning it acts to resist your force of motion no matter what.

- Kinetic friction generates heat & sound or both

Normal force

the force a surface exerts on a object

Fn / Fw = m x g → mass x gravity

g = 9.8 m/s2

How do you get an object at rest to begin moving?

You have to apply a force greater than the static friction that’s keeping the object in place

Momentum & Impulse

P = m x v → units = kgm/s

J / impulse = F x Δt → F x t_final - t_initial

F = force

Δt = change in time

J = F x Δt = Δp / momentum → J = mv_final- mv_initial

• If you apply force on an object it will gain some momentum

• Momentum in all collisions are always conserved never lost.

  Units for Impulse = n x s ****NOT n/s

Conservation of momentum equations

(M_1i)(V_1i) + (M_2i)(V_2i) = (M_1f)(V_1f) + (M_2f)(V_2f) → Used for elastic collisons

(M₁)(V₁) = (M₂)(V₂)

(M_1i)(V_1i) + (M_2i)(V_2i) = (M₁₊M₂) V_f → Used for inelastic collisions

P_{before =} P_after

Collisions

When an object in motion comes into contact w/ another object

Elastic Collisions

Kinetic energy & momentum is conserved

* NO ENERGY IS LOST

Equation: (M_1i)(V_1i) + (M_2i)(V_2i) = (M_1f)(V_1f) + (M_2f)(V_2f) → Used for elastic collisons

When objects collide / bounce off of eachother and seperate after collision.

Inelastic Collisions

Kinetic energy IS NOT conserved, but momentum is conserved

* ENERGY IS LOST in the form of sound, heat or internal energy of the new system

When an object in motion collides with another object at rest, and after the collision the objects stick together becoming one combined mass that travels at the same velocity

Equation = (M_1i)(V_1i) + (M_2i)(V_2i) = (M₁₊M₂) V_f → Used for inelastic collisions

When a force is applied over a longer interval of time

Amount of impulse / change momentum increases

if time is doubled, impulse is also doubled

When a force is applied over a shorter interval of time

Amount of impulse / change in momentum decreases

If time is havled, impulse is also halved

Power

units = watts

Equations = fd /t or w/t → force x distance / time

• Remember to gain power you have to put in a lot of work over time!!

  Power is the net force applied to an object w/ a particular average velocity

Work

W = fd = Δ ET → force x distance

ΔET = PE + KE + Q

PE = potential energy, m x g x Δh

KE = ½ mv²

Q = heat / internal energy

units = joules

Work is a change in energy

Potential Energy

Is energy stored in an object that could be used to do work.

ΔPE = m x g x Δh

Hooke’s Law

F_s = kx

F_s = force of spring

k = spring constant

x = change in distance of the spring (streched or compressed)

PEs = ½ kx²

Energy

* ENERGY IS ALWAYS CONSERVED NEVER CREATED NOR DESTROYED

Energy can also be converted into different forms

Ex: turning on a light bulb, electrical energy → light / heat energy

Ex 2: Eating food and riding a bike later in the day

chemical energy → mechanical energy

This means that PE = KE = W in certain circumstances

Ex 3: Holding a ball over a 10 foot building in let it fall to hit the ground potential energy → kinetic energy

Units = Joules

When an object is at the peak / greatest height

PE = highest magnitude / non zero

KE = 0 J

When an object is at its lowest point / no height

PE = 0 J

KE = non-zero J

Static Electricity

Occurs when an object obtains a total amount of positive or negative charge, creating an imbalance that wants to be returned to equilibrium

Atoms

Contains charged particles, positive protons and negative electrons

Law of Conservation of Electric Charge

You can never create a total electric charge. Instead, charge can only move from one place to another.

Coulombs Law

Symbol for charge = q | Units for charge = C / coulombs

One single electron = -1.60 × 10^-19 C

One single proton = 1.60 × 10^-19 C

* sign changes depending on the particle

K = 8.99×10^9 n x m² / c²

Electrostatic force

when radius increases, electrostatic force increases, Direct relationship.

Electrostatic forces can be attractive or repulsive, depending on the signs of the charges.

Electrostatic force is a vector.

Electric field

An electric field is a measurable effect generated by any charged object.

An electric field carries energy and passes it onto another charge object by exerting electric forces.

E = f / q

q = charge

f = force

E = electric field

E = K x q / r²

r = radius

k = electrostatic constant → 8.99×10^9

Electric field line show the magnitude and direction of the force exerted on any nearby positive test charge.

Positive charge

Electric field lines point outwards to signify that positive test charge is a repulsed by +Q

Negative charge

Electric field lines point inwards to signify that positive test charges attracted to -Q

Electric Dipole

Electric field lines go from positive charge to negative charge to show attraction, Two particles that generate their own electric field, we can add fields together to create a total electric field.

* Principle known as superposition

Four important properties of electric field lines

1) The field lines must be tangent to the direction of the field line at any point

2) the greater the line density the greater than magnitude of the field

3) lines ALWAYS START FROM POSITIVELY CHARGED OBJECTS AND END ON NEGATIVELY CHARGED OHJECTS

4) Lines never cross

Equilibrium

When electric charges are at equilibrium a = 0 m/s², Fnet = 0 N, E / Electric field = 0 N/C

• Since electric field represents electric forces acting on nearby charges when there is no force there is no electric fields.

Waves transfer

energy from one place to another

* ** WAVES DONT TRANSFER MATTER

Fundamental Forces

Strongest: Strong nuclear force → Binds protons & neutrons to create nucleus

2nd strongest: Electromagnetic force → Affects charged particles

2nd weakest: Weak nuclear force → Radioactive decay & converts neutrons → protons

Weakest force: Gravitational force → Attracts objects with mass

If a waves undergoes refraction, diffraction, or reflection

Wavelength always stays the same