Physics Flashcards
_______________
- measured in units (m, kg, s, K…)
- like numbers they can cancel out, be squared, & so on…
Quantities
_______________ quantities
- have magnitude only
Scalar quantities
_______________ quantities
- have both magnitude & direction
Vector quantities
True or false:
Mass is a scalar. Weight is a vector because it is a force & has both magnitude & direction
True
_______________
- (linear) motion is a net displacement of either a point mass or all parts of a body moving along parallel lines (or arcs)
Translational
_______________
- occurs in response to forces acting through the object center of mass (even though the force may actually be off-center)
Linear acceleration
_______________
- motion is circular about an axis with no net displacement
Rotational motion
_______________
- a vector
- refers to net movement in 1 or more dimensions
- shortest distance between initial & final position (may be different from total distance traveled)
Displacement
____________ measures displacement over time
Velocity
____________ measures distance traveled over time
Speed
Speed is ____________ because direction is unimportant
Scalar
Velocity is a ____________ because direction is important
Velocity
____________ velocity can be derived by calculus for very short time intervals
Instantaneous velocity
_________________
- to add 2 vectors graphically, place the tail of 1 vector at the tip of the other, maintaining the original orientations.
Graphic addition
__________ quantities can also be subtracted and multiplied to generate dot & cross products
Vector
_______________
- change in velocity per unit time
Acceleration
_______________
- A push or pull on a body
- It can act at a distance or through contact with the body
Force
_______________
- exists when a body is at rest or moving at a constant velocity
- Net external forces are equal to zero
Equilibrium
_______________
- objects continue to do what they have been doing, either being at rest, or moving in a straight line at constant velocity (unless acted on by external unbalanced forces)
Newtons first law
_______________
- resistance to change
- Quantified mass
Inertia
An object will not rotate or does so at constant angular velocity, unless acted on by ___________
Torque (also called a moment)
True or false
Forces are always vector quantities
True
_______________
- if a body is not in equilibrium, it must be accelerating due to the action of one or more unbalanced forces
Newtons second law
_______________
- forces exist in pairs
- For every action there is an equal and opposite reaction
- If object A exerts a force on object B then object B exerts an equal & opposite force on object A
Newtons third law
True or false
To analyze motion, all forces and any related torques must be considered
True
If force is applied at an angle other than 90 degrees then torque is ____________
Reduced
Forces applied to a rigid body some distance from the axis of rotation causes rotation about the axis or the tendency to rotate called ____________
Torque
If not rotating or velocity is constant then the net sum of all torques must be __________
Zero
If a torque is applied on an unconstrained body then it rotates around the _______________
Center of mass
True or false
In some cases the center of mass is not found on the physical body
True
When 2 bodies are in contact then the ____________ is the component perpendicular to the surfaces in contact
Normal force
Molecular interactions between 2 surfaces results in ____________
Friction force
The magnitude of ____________ depends on the normal force and a constant coefficient of friction “ų” unique to the 2 materials (“ų” varies between 0-1 in most cases but can be larger & size of the area of contact is not important)
Frictional force
True or false
Frictional forces always oppose motion
True
_______________
- can be converted from 1 form to another & transferred from 1 object to another, but cannot be created or lost
- A scalar quantity
- many forms (chemical, nuclear, electromagnetic, elastic, gravitational)
Energy
The total of ___________ & ____________ is mechanical energy
Kinetic energy
Potential energy
_______________
- The energy of motion
1/2mv^2
Kinetic energy
_______________
- Energy associated with position
- Maybe within a gravitational, electric, or magnetic field or from intermolecular forces
Potential energy
_______________
- The rate at which work is done
Power
_______________
- result of a force acting on a body such that there is a displacement in the direction of the force
- Measured in Joules
Work
When force is constant, ____________ equals force times displacement
- The product of the 2 vectors (force & displacement) count, only the displacement in the direction of the force & equals F•xcosθ (θ is the angle between the vectors)
Work
Simple machines either change the direction or magnitude of an applied __________
Force
True or false
If the magnitude of the force has changed, then the result is a mechanical advantage. The ratio of the output force to the input force equals the mechanical advantage.
Mechanical advantage = F(out) / F(in)
True
_______________ theorem
- The amount of work done on an object is equal to the change in kinetic energy of the object
Work Kinetic energy theorem
_______________
- forces that conserve mechanical energy (KE & PE)
- gravity, electrostatic force, & spring force (all store energy)
- work done on an object depends only the initial & final positions (not on the path taken to get there)
- loops —> no work done by the conservative force (net movement is 0)
Conservative forces
_______________
- friction, viscous force like air resistance, & magnetic force
- Result in some energy lost (heat, sound, or wakes)
- Vary with velocity & result in energy loss by the object on which the force is acting
Nonconservative forces
True or false
When a body is acted on by both conservative & nonconservative forces, then the work done by the nonconservative force equals the change in kinetic energy plus change in potential energy
True
_______________
- The kinetic energy of molecular motion
- Measured in calories
Heat
3 mechanisms of heat transfer
____________
____________
____________
Conduction
Convection
Radiation
_______________
- A form of heat transfer that requires physical contact and resembles chemical diffusion
- Greater thermal energy of motion in one body is conveyed to a second body via molecular collisions
Conduction
_______________
- A form of heat transfer in which movement of a fluid can transport heat energy
- Maybe forced or natural
Convection
_______________
- form of heat transfer unique because no medium is necessary
- Heat can travel vast distances through space in the form of electromagnetic waves
Radiation
________ motion
- Repeats a regular cycle (1 cycle = 360°)
- Oscillations occur around an equilibrium position (rest)
- Can be described by a sine function
Periodic motion
_______________
- cycles per second
- Reciprocal of a period
Frequency
_______________
- maximum distance traveled from the rest position in periodic motion
Amplitude
_______________
- distance between a point & corresponding point in next cycle
Wavelength
_______________
- Location in the 360° cycle
Phase
Colliding waves
- when 2 peaks coincide the amplitudes sum causing ____________ interference
- When a trough coincides with a peak the amplitude cancel causing __________ interference
Constructive interference
Destructive interference
_______________
- periodic motion that has transport energy
Waves
_______________
- The speed at which the disturbance is transmitted
Propagation velocity
True or false:
Most waves require a physical medium. Light is unusual in that it does not. Properties of the medium, determined speed but not period, frequency, or amplitude
True
Mechanical waves can be generated & propagated in deformable materials.
2 types of waves : _______________ & ______________
Transverse
Longitudinal
______________ waves
- wavelike motion occurs in a direction at right angles to the direction of the wave
- the disturbance is propagated along the length carrying energy & momentum horizontally
Transverse
_______________ waves
- aka compression waves
- movement of the wave & the individual parts of the object is in the same or opposite direction
Longitudinal waves
True or false
in air, the sound wave is produced by the back-and-forth motion of individual air molecules moving in the direction of the wave
True
Sound is a longitudinal wave where pressure variations called ____________ & ___________ are transmitted outward radially from the source
Compressions
Rarefactions
Longitudinal waves are often generated by ____________ vibrations of a solid body which impresses those vibrations on the air molecules
Mechanical
_______________
- the perception of frequency
Pitch
_______________
- beyond 20,000 Hz
- used for medical imaging
Ultrasound
True or false
Sound requires a medium such as air & it cannot be transmitted in a vacuum
True
Speed of sound is slowest in ________ (340m/s) , higher in ________ (1,500m/s) , & highest in ________ (5,000m/s)
Gases
Liquids
Solids
Why does the sound travel faster in solids & liquids when compared to gases?
The particles are closer so energy is transmitted more quickly
When sound moves from 1 medium to another, some energy is reflected backward which can be used to visualize structures
- most significant when it’s between solid & liquid because almost all of the sound echoes off the boundary
- the difference in density between the 2 media determines the extent of reflection
_______________ imaging utilizes these concepts
Ultrasound
_______________
- When an object moves as fast or faster than sound then it causes an abrupt disturbance in the medium (sonic boom)
Shock wave
_______________
- When sound travels through a medium, the viscosity of the medium result in energy losses (friction)
- As more energy is lost, the sound becomes fainter
Attenuation
- different materials have different degrees of attenuation
- attenuation varies with frequency (longer wavelengths lose less energy)
- attenuation is a specific type of damping (when objects oscillate to & fro then frictional losses cause an exponential decay in amplitude with time)
_______________
- if a longitudinal wave is propagated down an air-filled pipe then the wave is reflected like waves on a stretched string —> standing waves in the pipe
Resonance
The lowest tone an instrument can make is the ____________ frequency
____________ have higher frequencies (integral multiples of the fundamental)
Fundamental
Harmonics
Sound has 2 different measures of power
____________
____________
Total power (radiating from the source)
Intensity (power per unit area at given distance that can be absolute or relative)
_______________
- quantify sound intensity
- a logarithmic scale comparing sounds to the faintest sound a human can detect
Decibels
- a 100x increase in intensity —> 20 dB increase
- the perception of intensity is not the same as the actual intensity & a 10x increase in intensity is perceived as being 2x as loud
_____________ effect
- the apparent increase or decrease in frequency when the source & observer are moving toward or away from each other
- observer & source move closer then the apparent frequency rises
- observer & source move apart then the apparent frequency drops
Doppler effect
_______________
- include both liquids & gases
- molecules are free to move with respect to one another (not constrained)
Fluids
_______________
- a measure of how much matter is packed into a given volume (mass/volume)
- indirectly proportional to the cube of the distance between molecules (more distance between molecules means less dense)
Density
