Welcome to Resourcify! Discover a wealth of meticulously crafted teaching materials for educators, students, and parents. Whether you're a seasoned teacher, a student seeking support, or a parent supplementing home learning, Resourcify is your versatile destination for quality resources. Explore, download, and enhance your educational journey with us! For questions or assistance, contact us at resourcify321@gmail.com, and we'll promptly respond!
Welcome to Resourcify! Discover a wealth of meticulously crafted teaching materials for educators, students, and parents. Whether you're a seasoned teacher, a student seeking support, or a parent supplementing home learning, Resourcify is your versatile destination for quality resources. Explore, download, and enhance your educational journey with us! For questions or assistance, contact us at resourcify321@gmail.com, and we'll promptly respond!
A Level Physics worksheet containing questions about the lesson: The Gas Laws
Model Answers Included
This worksheet covers the following content:
-Boyle’s law including techniques and procedures used to investigate it
-Pressure law including an experiment to investigate it and estimate absolute zero
-Charles’ law
This is tailored for the OCR A specification, however, the versatile nature of this resource makes it suitable for other exam boards too.
This resource is designed to help students apply their knowledge to questions. This active revision technique ensures that the worksheet will be very useful for students, and will act as a vital revision tool.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
A Level Physics worksheet containing questions about the lesson: Specific Heat Capacity & Latent Heat
Model Answers Included
This worksheet covers the following content:
-specific heat capacity of a substance; the equation E = mcΔT
-an electrical experiment to determine the specific heat capacity of a metal or a liquid
-specific latent heat of fusion and specific latent heat of vaporisation, E = mL
-an electrical experiment to determine the specific latent heat of fusion and vaporisation
This is tailored for the OCR A specification, however, the versatile nature of this resource makes it suitable for other exam boards too.
This resource is designed to help students apply their knowledge to questions. This active revision technique ensures that the worksheet will be very useful for students, and will act as a vital revision tool.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
A Level Physics worksheet containing questions about the lesson: States of Matter & Temperature
Model Answers Included
This worksheet covers the following content:
-thermal equilibrium
-absolute scale of temperature (i.e. the thermodynamic scale) that does not depend on property of any particular substance
-temperature measurements both in degrees Celsius (°C) and in kelvin (K)
-T(K) ≈ θ(°C)+273
-solids, liquids and gases in terms of the spacing, ordering and motion of atoms or molecules
-simple kinetic model for solids, liquids and gases
-Brownian motion in terms of the kinetic model of matter and a simple demonstration using smoke particles suspended in air
-internal energy as the sum of the random distribution of kinetic and potential energies associated with the molecules of a system
-absolute zero (0 K) as the lowest limit for temperature; the temperature at which a substance has minimum internal energy
-increase in the internal energy of a body as its temperature rises
-changes in the internal energy of a substance during change of phase; constant temperature during change of phase.
This is tailored for the OCR A specification, however, the versatile nature of this resource makes it suitable for other exam boards too.
This resource is designed to help students apply their knowledge to questions. This active revision technique ensures that the worksheet will be very useful for students, and will act as a vital revision tool.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Universe Evolution for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-estimation for the age of the universe; t ≈ 1/H0
-evolution of the universe after the Big Bang to the present
-current ideas; universe is made up of dark energy, dark matter, and a small percentage of ordinary matter.
This lesson includes:
-A full presentation including an example question with a worked solution.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers the Big Bang Theory for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-the cosmological principle; universe is homogeneous, isotropic and the laws of physics are universal
-Doppler effect; Doppler shift of electromagnetic radiation
-Doppler equation: Δλ/λ ≈ Δf/f ≈ v/c for a source of electromagnetic radiation moving relative to an observer
-Hubble’s law; v ≈ H0 d for receding galaxies, where H0 is the Hubble constant
-model of an expanding universe supported by galactic red shift
-Hubble constant H0 in both km s–1 Mpc–1 and s–1 units
-the Big Bang theory
-experimental evidence for the Big Bang theory from microwave background radiation at a temperature of 2.7 K
-the idea that the Big Bang gave rise to the expansion of space-time
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Stellar Spectra for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-energy levels of electrons in isolated gas atoms
-the idea that energy levels have negative values
-emission spectral lines from hot gases in terms of emission of photons and transition of electrons between discrete energy levels
-the equations hf = ΔE and hc/λ = ΔE
-continuous spectrum, emission line spectrum and absorption line spectrum
-transmission diffraction grating used to determine the wavelength of light
-the condition for maxima: dsinθ = nλ, where d is the grating spacing
-different atoms have different spectral lines which can be used to identify elements within stars
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Stellar Radiation & Luminosity for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-use of Wien’s displacement law λmax ∝ 1/T to estimate the peak surface temperature (of a star)
-luminosity L of a star; Stefan’s law L = 4πr²σT⁴ where σ is the Stefan constant
-use of Wien’s displacement law and Stefan’s law to estimate the radius of a star.
-Hertzsprung–Russell (HR) diagram as luminosity-temperature plot; main sequence; red giants; super red giants; white dwarfs.
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Stellar Evolution (Life Cycle of Stars) for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-formation of a star from interstellar dust and gas in terms of gravitational collapse, fusion of hydrogen into helium, radiation and gas pressure
-evolution of a low-mass star like our Sun into a red giant and white dwarf; planetary nebula
-characteristics of a white dwarf; electron degeneracy pressure; Chandrasekhar limit
-evolution of a massive star into a red super giant and then either a neutron star or black hole via a supernova
-characteristics of a neutron star and a black hole
This lesson includes:
-A full presentation with visual aids.
-A worksheet with model answers, perfect to set as homework.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Astronomical Distances for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-distances measured in light-years (ly) and parsecs (pc)
-stellar parallax and how it can be used to find distances in parsecs (pc)
-the equation p = 1/d, where p is the parallax in seconds of arc and d is the distance in parsecs
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers The Solar System for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-the terms planets, planetary satellites, comets, solar systems, galaxies and the universe
-distances measured in astronomical unit (AU)
This lesson includes:
-A full presentation including clear visual aids and diagrams.
-A worksheet with model answers, perfect to set as homework.
-Editable PowerPoint and Word document for easy customisation.
(Please note that this specific lesson serves as a brief introduction to the basics within the broader topic of astrophysics and cosmology)
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Planetary Motion (Motion of Masses in Gravitational Fields) for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-Kepler’s three laws of planetary motion
-the centripetal force on a planet is provided by the gravitational force between it and the Sun
-the equation T² = (4π²/GM)r³ (T² ∝ r ³) including derivation from first principles
-geostationary orbit; uses of geostationary satellites
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Gravitational Potential & Energy for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-gravitational potential at a point as the work done in bringing unit mass from infinity to the point.
-gravitational potential is zero at infinity
-gravitational potential Vg =-GM/r at a distance r from a point mass M
-changes in gravitational potential
-force–distance graph for a point or spherical mass; work done is area under graph
-gravitational potential energy E = mVg = - GMm / r at a distance r from a point mass M
-escape velocity.
This lesson includes:
-A full presentation including 3 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Gravitational Field Strength for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-gravitational field strength; g = F/m
-gravitational field strength g = -(GM) / r² for a point mass (inverse square law)
-gravitational field strength is uniform close to the surface of the Earth and numerically equal to the acceleration of free fall.
This lesson includes:
-A full presentation including 3 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Gravitational Fields for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-gravitational fields are due to objects having mass
-modeling the mass of a spherical object as a point mass at its centre
-gravitational field lines to map gravitational fields (uniform and radial)
-the concept of gravitational fields as being one of a number of forms of field giving rise to a force
-Newton’s law of gravitation; F = -(GMm)/r² for the force between two point masses (inverse square law)
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Damping (Free & Forced Oscillations) for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-free and forced oscillations
-the effects of damping on an oscillatory system
-observe forced and damped oscillations for a range of systems
-resonance; natural frequency
-amplitude-driving frequency graphs for forced oscillators
-practical examples of forced oscillations and resonance
This lesson includes:
-A full presentation with clear visual aids and diagrams.
-A worksheet with model answers, perfect to set as homework.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Simple Harmonic Motion for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-displacement, amplitude, period, frequency, angular frequency and phase difference
-simple harmonic motion; defining equation a =-ω²x
-techniques and procedures used to determine the period/frequency of simple harmonic oscillations
-solutions to the equation a = -ω²x e.g. x = Acosωt or x = Asinωt
-velocity v = ± ω √ (A² - x²) hence vmax = ωA
-the period of a simple harmonic oscillator is independent of its amplitude (isochronous oscillator)
-graphical methods to investigate simple harmonic motion (mass of spring system).
-interchange between kinetic and potential energy during simple harmonic motion
-energy-displacement graphs for a simple harmonic oscillator
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Centripetal Force & Acceleration for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-a constant net force perpendicular to the velocity of an object causes it to travel in a circular path
-centripetal acceleration; a = v²/r ; a = ω²r
-centripetal force; F = mv²/r ; F = mω²r
-techniques and procedures used to investigate circular motion using a whirling bung.
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers Circular Motion for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-the radian as a measure of angle
-period and frequency of an object in circular motion
-angular velocity ω, ω =2π/T or ω = 2πf
-constant speed in a circle; v = ωr
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers The Internal Energy of an Ideal Gas for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-general characteristics of the Maxwell-Boltzmann distribution.
-internal energy of an ideal gas.
-the derivation of the equation 1/2 mc² = 3/2 kT
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.
This resource is a complete lesson that covers The Pressure of an Ideal Gas for the OCR A Level Physics A course. However, it is useful for other exam boards too.
This lesson teaches the following content:
-model of kinetic theory of gases (assumptions of the model)
-pressure in terms of kinetic theory of gases
-the equation pV = 1/3 Nmc² , where N is the number of particles (atoms or molecules) and c² is the mean square speed
-root mean square (r.m.s.) speed and mean square speed
This lesson includes:
-A full presentation including 2 example questions with worked solutions.
-A worksheet with model answers, perfect to set as homework.
-Clear visual aids and diagrams to simplify complex concepts.
-Editable PowerPoint and Word document for easy customisation.
Click on the links below to check out our FREE A Level Physics resources:
Mass, Weight & Force Basics Lesson
Net Forces & Equilibrium Lesson
Moments & Torques Lesson
Drag & Terminal Velocity Lesson
Density, Pressure & Upthrust Lesson
We really appreciate feedback on our resources so if you kindly leave a review down below, you will be able to claim any resource (up to the value of this resource) from our shop for FREE. Just email resourcify321@gmail.com with your username and your chosen resource. Your chosen resource will be sent to you within 24 hours.