Physics MCAT

Vector Vs Scalar

Vector

• Have Magnitude and direction

Scalar

• Have magnitude no direction

Vector Examples

• Velocity

Scalar Examples

• Speed

Velocity

• Average Velocity

  • Formula V = d/t

• Instantaneous Velocity

  • You can calculate the speed of the object at anytime in point.

Acceleration

Change in velocity

• V= at

• We can drive these equations on the photo from V = at

Acceleration Equations

Three Formulas are derived from each other

Acceleration Example Question:

1. A ball is thrown horizontally off a building that is 45 meters high. How long does it take to hit the ground (ignore air resistance)

2. How fast is the ball going when it hits the ground?

We can use Formula = D = ½ at²

• ^{When you divide something by 2 is the same as when you multiply by ½.}

Newton’s Law Of Motion

1. An object at rest will remain at rest unless we apply unbalanced force to it

2. An object in motion will remain in motion unless unbalanced force acts on it

3. For every action there is an equal and opposite reaction

SI Units

Force Unit : Newton (N)

• Formula: F = ma

• Newton (N) = (kg) (m/s²)

Work Unit: Joules (J)

• Formula : W = Fd

• Joules (J) = Newton (N) = (kg) (m/s²) x Meters (m)

Power Unit: Watt (W)

• Formulas: P = W/t

• Watt (W) = Joules (J)/ S

• Another Formula: P = FV

Density Unit (g/cm³ OR kg/m³)

• Formula: ρ = m/v

• ρ = kg/m³

• ρ = g/cm³

Pressure Unit: Pascal (Pa)

• Formula: P = F/A

• Pa = N/m²

1. A 70 kg man climbs up two flights of stairs for a total of 15 meters. How much work did he do?

2. If it took him 20 seconds to climb these stairs, How much power did it require?

Formula:

• F = ma

• W = Fd

• P = W/t

Object sliding comes to a stop when friction force acts on it

• Coefficient of friction is is a constant and unitless

• Normal force is the equal and opposite force that is pushing an object

  • F = ma

    • Example: A cup in a table has two forces, one pushing the table down and the other is the Normal force that acting on the opposite

Static Friction

• Static Friction

  • Trying to move a refrigerator and it doesn’t move the first time and then you put more force until it suddenly moves. This happens because there must be opposite force acting on the refrigerator to move

Friction Question

Energy

• Energy is the ability to do work

• Energy can be stored, used and interconvert different types of energies

Conservation Energy: Energy can neither be neither be created or destroyed it can only be converted from form to another

Types of Energy

Potential Energy - Height

• Gravitational Energy

  • High up, ability to fall

  • Formula: PE = mgh

• Elastic Energy

  • Spring compressed - storing PE energy and opposite is true

  • Formula: PE = ½ Kx²

Kinetic Energy - motion

• Motion of particles

• Example: Heat

  • Heat is motion of particles

  • Formula: K = ½ mv²

Picture: A hill - a ball at the top of the hill not moving has a zero kinetic energy and 100% Potential, when in the middle it’s 50/50 (PE = KE)

A stationary ball is released at the top of a 20m slope. What will be the velocity of the ball at the bottom of this hill

Formula: K = ½ mv²

Levers and Torque (moment)

Torque (moment) - is the force that causes objects to return or rotate

• Formula : 𝜏 = Fd

• 𝜏_{1 =} 𝜏₂

Torque (𝜏) practice question #1

Torque (𝜏) practice question #2

Density

Density is much mass is present in a given volume

• An object that is more dense in water will sink in water and an object that is less dense in water will float in water

• Density of water = 1

• Relative Density (specific gravity ) = Calculated relative to water

  • tells you what percentage of object will sink or float in water

Density practice questions

Mass

Amount of a matter that is present in an object

Pressure

Hydrostatic Pressure

Hydro(water) static (stationary) - water is not moving.

• Measuring pressure when water is not moving at different level of how deep the water is

Pascal’s Law

Types of Radioactive Decay

1. Alpha Decay

2. Beta Minus Decay

3. Beta Plus Decay

4. Gamma Decay

Alpha Decay

Releases a He atom (2 protons and 2 neutrons)

Atomic # -2

Mass # -4

Beta Minus (—)

A Neutron turns into a proton and electron, with the electron being realized

Atomic # +1

Mass # doesn’t change

Beta Plus (+)

A proton turns into a neutron and positron with the positron being released

Atomic # -1

Mass # doesn’t change

Gamma Decay

Energy is released, atom doesn’t change otherwise

Sound travel most Fastest

Solid —> Liquids —> Gas

• The speed of sound is greatest by far in a solid because of the strong intermolecular bonds and close proximity of the molecules. Because the temperatures are close to each other (and even favor iron slightly), iron will have the highest sound speed.

Sound In a Vacuum

Sound doesn’t travel in vacuums

Light travels fastest at

Vacuum —> Air —> Water —> Glass

When a light wave and a sound wave pass from air to glass, what changes occur in their speeds?

Light slows down: Sounds Speeds up

Light slows down because the index of refraction in the glass is greater than in the air. The index is a measure of the ratio of the velocity in air to the velocity in the medium. For sound the speed becomes greater because the speed of sound in a solid is much greater than in air (the glass has stiff rigid bonds which gives rise to a speed more than 10 times greater than in air).

A glass fiber carries a light digital signal long distances with a minimum loss of amplitude. What optical property of glass allows this phenomenon?

Reflection

Light can be carried along a distance within a transparent material by means of total internal reflection.

Hydrostatic Pressure equation

p = pgh

A question using Hydrostatic Pressure equation:

• If the second floor and the top floor of a building are separated by a distance of 100 m, what is the approximate difference between the air pressures of the two levels?  (Note: Air density = 1.2 kg/m³ and gravitational acceleration = 10 m/s². Neglect the compressibility of air.)

Pressure is given by (density) • g • (height) if density does not change. This is approximately true for small atmospheric height differences, such as 100 m. The pressure difference will be given by

(density) • g • (change in height)

or (1.2)(10)(100) = 1200 N/m².

A question using Hydrostatic Pressure equation:

• What is the difference in pressure between two points that are separated by a vertical distance of 0.25 m in a tank of water? (Note: The density of water is 1,000 kg/m³, and g = 10 m/s².)

The difference in pressure in a fluid on Earth is:
(density of fluid) × g × (change in height) = (1000)(10)(0.25) = 2500 N/m².

Myopia (Nearsightness)

Common vision condition in which close objects look clear but far objects look blurry

• Light doesn’t reach on the back of the eye (retina)

• Diverging (Concave lenses)

Hyperopia (Farsightness)

Common vision condition in which far objects look clear but close objects look blurry

• Light goes too far and passes the back of the eye (retina)

• Converging (convex lens

Astigmatism

Common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision

• Front surface of the eye (cornea) or the lens inside the eye has mismatched curves.

• Cylindrical lens

Focal Length Equals

The space between Focal Point and Lens

Focal Length is Positive and negative for lenses and images

Lens:

• + converging

• - Diverging

Image:

• + Real

• - Virtual

1. Converging (convex Lens)

If the object is away from the Focal point you get

• Real Image

• Inverted image

2. Converging (convex Lens)

If the object is between the Focal point and lens you get

• Upright magnified image

• Virtual magnified image

Diverging (Concave Lens)

Object is located anywhere

• Virtual smaller image

• Upright smaller image

Thin Lens Equation

If an electron goes from the n = 2 shell to the n = 3 shell:

The energy of an electron in orbit n = 3 is less negative or greater than the energy in orbit n = 2. Thus energy is required to make the transition from n = 2 to n = 3 and the atom gains energy.

MNEMONIC: As electrons go from a lower (n = 1) energy level to a higher (n= 3) energy level, they get AHED: Remember the Opposite

• Absorb light

• Higher potential

• Excited

• Distant (from the nucleus)

Energy increase Photon Absorbed

Reflections and Refractions

• Happens when light changes medium

• Light encounters change in medium

Light Reflection and Transmission

Light can either be reflected or transmitted

Reflection

• Theta of Incident = Theta reflection

Transmitted

• Travels in continous

Incident Light wave

Is the light approaching the medium

Change in Medium of light

Causes light to bend

• When light travels from thin material like air to think material like glass it bends towards the normal and angle decreases

Refractive index

n is always equal to 1 or greater than 1