Biophysics First Level Quiz

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Questions and Answers

What is the unit of rate change of velocity in cgs?

  • cm.s−2 (correct)
  • m.s−2
  • kg.s−2
  • g.s−2

What is the dimension of force gradient?

  • MLT−1
  • ML2T−2
  • MLT−2
  • MT−2 (correct)

What is the unit of force gradient in MKS units?

  • g.s−1
  • Kg.s−2 (correct)
  • g.s−2
  • Kg.s−1

Which of the following best describes numeric constants?

<p>Have no dimensions and no units (B)</p> Signup and view all the answers

What is the expression for the gradient of a quantity?

<p>Quantity/Distance (B)</p> Signup and view all the answers

What is the primary purpose of dimensional analysis in the context of mathematical equations?

<p>To ensure equations have the correct dimensions (C)</p> Signup and view all the answers

Which of the following equations describes a linear relationship in physics according to dimensional analysis?

<p>X = V0 t + a t^2 (A)</p> Signup and view all the answers

In the equation X = V0 t + a t^2, what does V0 represent?

<p>The initial velocity (B)</p> Signup and view all the answers

What type of term is a t^2 in the equation X = V0 t + a t^2?

<p>Quadratic term (C)</p> Signup and view all the answers

Which dimension does the left-hand side of the equation X = V0 t + a t^2 represent?

<p>Displacement (D)</p> Signup and view all the answers

What is the formula for calculating density?

<p>ρ = m/V (C)</p> Signup and view all the answers

What are the correct units for density in the context provided?

<p>ML−3 (C), Kg.m−3 (D)</p> Signup and view all the answers

What is the dimensional formula for density?

<p>ML−3 (D)</p> Signup and view all the answers

In the equation ρ = m/V, if the mass doubles while the volume remains constant, what happens to the density?

<p>Density doubles (D)</p> Signup and view all the answers

Which of the following represents a common mistake in understanding density?

<p>Density is always constant for a substance (A), Density is mass multiplied by volume (B), Density decreases as temperature increases (C), Density is the same at all states of matter (D)</p> Signup and view all the answers

What is the unit of energy in the given context?

<p>Joule (A)</p> Signup and view all the answers

How is energy measured in the cgs system?

<p>Gram-centimeter squared (C)</p> Signup and view all the answers

What calculation is represented by the term '1000 x 10000 x 10^7'?

<p>Energy in cgs units (C)</p> Signup and view all the answers

Which of the following describes the relationship between Joules and cgs units?

<p>Joules are larger than cgs units (D)</p> Signup and view all the answers

What dimensional formula is used for energy according to the provided content?

<p>g.cm^2 (B)</p> Signup and view all the answers

What is the formula for acceleration?

<p>a = v/t (D)</p> Signup and view all the answers

In the formula for force, F = m × a, what do the symbols represent?

<p>Force is mass times acceleration (A)</p> Signup and view all the answers

What are the SI units of acceleration?

<p>m/s² (C)</p> Signup and view all the answers

What are the dimensional units for force?

<p>MLT−2 (D)</p> Signup and view all the answers

What does the symbol 'v' represent in the acceleration formula?

<p>Velocity (D)</p> Signup and view all the answers

What is the relationship between Joules and ergs?

<p>1 Joule = 10^7 ergs (A)</p> Signup and view all the answers

What is the formula for calculating velocity?

<p>Velocity = x/t (B)</p> Signup and view all the answers

Which dimension represents velocity?

<p>LT^-1 (C)</p> Signup and view all the answers

What is the density formula?

<p>Density = m/V (A)</p> Signup and view all the answers

What unit is equivalent to 1 Kg in g?

<p>10^3 g (B)</p> Signup and view all the answers

What is the definition of a gradient?

<p>Change in quantity with respect to distance (A)</p> Signup and view all the answers

Which statement about the refractive index is true?

<p>It is dimensionless and has no unit (D)</p> Signup and view all the answers

The dimension of rate change of velocity is represented as?

<p>LT^-2 (A)</p> Signup and view all the answers

To convert Km/h to m/s, which factor is used?

<p>0.27778 (D)</p> Signup and view all the answers

What is the density dimension?

<p>ML^-3 (C)</p> Signup and view all the answers

Flashcards

Rate of velocity change cgs unit

The rate at which velocity changes, measured in centimeters per second squared (cm⋅s⁻²).

Gradient definition

Rate of change of a quantity over distance.

Force gradient

Rate of change of force over distance.

Force gradient dimensions

Mass times length per time squared (MLT⁻²).

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Numeric constant

A constant with no units or dimensions.

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Erg

A unit of energy in the centimeter-gram-second (cgs) system. 1 Joule = 10^7 erg

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Joule

The standard unit of energy in the International System of Units (SI). 1 Joule = 10^7 erg

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Velocity

The rate of change of position with respect to time.

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Velocity dimension

Length (L) divided by Time (T), often written as LT−1

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Density

Mass per unit volume.

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Density dimension

Mass (M) divided by Length^3 (L^3), or ML^-3

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Ratio

A comparison of two quantities of the same type.

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Rate

A quantity that changes over time.

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Gradient

A change in a quantity with respect to distance

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Refractive index

The ratio of the speed of light in a vacuum to its speed in a medium.

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Dimensional Analysis

A method to check the correctness of physics equations by analyzing the dimensions of the variables.

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Equation correctness

Verifying if an equation describing a physical experiment is dimensionally consistent.

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Dimensions of L.H.S.

Identifying the physical units (e.g., length, time) on the left-hand side of a physics equation.

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Equation: X = V₀t + ½at²

A physics equation that relates displacement (X), initial velocity (V₀), time(t), and acceleration(a).

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Physical Experiment

An experiment to obtain results for a physics equation such as X = V₀t + ½at²

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Density Formula

Density is mass divided by volume.

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SI Unit of Density

Kilograms per cubic meter (kg/m³).

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Density Units in CGS

Grams per cubic centimeter (g/cm³).

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Density Dimension

Mass per unit volume.

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Density Symbol

The Greek letter rho (ρ).

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Energy Unit

A unit of measurement for energy, for example in Joules or erg

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Joule (SI)

Unit of energy in the International System of Units (SI).

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Erg (cgs)

Unit of energy in the centimeter-gram-second system (cgs).

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Energy Conversion

Relationship between energy units in different systems.

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Energy in cgs

Energy measure in cgs units, g⋅cm²/s² (erg).

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Acceleration Unit

The unit of acceleration, often measured in meters per second squared (m/s²).

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Force Formula

Force equals mass times acceleration (F = ma).

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SI Unit of Force

The unit of force in the International System of Units (SI).

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Acceleration Dimension

The physical dimensions of acceleration.

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Force Dimension

Represents how force relates to mass and acceleration.

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Study Notes

Introduction to Biophysics

  • Course: Biophysics
  • Level: First Level
  • Year: 2024-2025
  • Instructors: Dr. Nermin Ali, Dr. Enas Lotfy
  • Course Code: FAC-104

Dimensions and Units

  • SI Units: A standardized system of units
  • Basic Quantities: Length (L), Mass (M), Time (T), Electric Current (I), Temperature (Θ), Amount of substance (N), Luminous intensity (J)
  • Derived Quantities: Calculated from basic quantities (e.g., velocity, acceleration, force, pressure).
  • Scalar Quantities: Described only by magnitude (e.g., price, age, speed).
  • Vector Quantities: Described by both magnitude and direction (e.g., force, velocity)
  • Units: Standard measurements for dimensions (e.g., meters for length).

Basic Definitions

  • Basic Quantity: A quantity that cannot be expressed in terms of other quantities.
  • Basic quantities include: Length, Mass, Time.
  • Other basic quantities include: Electric current, Luminous intensity, mole, temperature

Derived Quantities

  • Derived Quantity: A quantity that can be expressed in terms of more than one basic quantity.
  • Example quantities: Velocity, acceleration, force, pressure

Scalar Quantities

  • A quantity defined only by its magnitude.
  • Examples include: price, age, speed.

Vector Quantities

  • A quantity defined by both magnitude and direction.
  • Examples include: force, velocity.

Difference Between Dimension and Unit

  • Dimension: Represents the physical nature of a quantity (e.g., length).
  • Unit: Represents the standard for measuring a dimension (e.g., meters).
  • Dimension defines what is being measured, while the unit defines how it is measured.

SI Base Quantities and Units

Quantity SI Unit Symbol
Length Meter m
Mass Kilogram kg
Time Second s
Electric Current Ampere A
Temperature Kelvin K
Amount of substance Mole mol
Luminous intensity Candela cd

Area and Volume

  • Area: Length × Width, dimension [L2]
  • Volume: Length × Width × Height, dimension [L3]

Dimension and Units of Basic and Derived Quantities

  • Provides formulas and dimensions for various quantities (mass, length, time, area, volume, velocity, acceleration, force, pressure, viscosity, density.) and their units in MKS and CGS.

Converting Quantities from One System to Another

  • Explaining how to convert quantities (like force, energy and velocity) from one system like MKS (meter, kilogram, second) to others like CGS (centimeter, gram, second).
    • Shows the conversions

Ratio, Rate, Gradient

  • Ratio: Comparison of similar quantities.
  • Rate: Change in a quantity over time.
  • Gradient: Change in a quantity over distance.

Refractive Index

  • A ratio representing the change in the velocity of light as it passes from one medium to another.
  • It has no dimensions and no units.

Velocity

  • The rate of change of displacement with respect to time.
  • Dimension: LT-1
  • Units: m/s (MKS) or cm/s (CGS)

Density

  • The ratio of mass to volume, dimension: ML−3
  • Units: kilograms per cubic meter (MKS) or grams per cubic centimeter (CGS)

Difference between Numeric and Physical Constants

  • Numeric constant: Does not have dimensions nor units
  • Physical constant: Has both dimension and units.

Dimensional Analysis

  • A technique to check the consistency of equations.

Gravitational Constant

  • The constant in Newton's law of universal gravitation.
  • Dimension: M-1L3T-2.
  • Unit in MKS: kg-1m3s-2.
  • Unit in CGS: g-1cm3s-2

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Lecture 1, Biophysics, HUE AHST, 2024

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