Studied by 7 people
interaction
any event in which two or more objects exert forces on each other
newton, N
derived SI unit of force, 1 N = 1 kgms⁻²
mass
a measure of an object’s resistance to a change of motion (inertia)
kilogramme, kg
SI unit of mass (fundamental)
weight, F
gravitational force acting on a mass, F = mg
gravitational field strength, g
the gravitational force per unit mass (that would be experienced by a small test mass placed at that point), g = F/m (SI unit: Nkg⁻¹), numerically equal to the acceleration due to gravity
centre of mass
average position of all the mass of an object, the mass of an object is distributed evenly either side of any plane through its centre of mass
force meter
instrument used to measure forces, also sometimes called a newton meter or a spring balance
calibrate
put numbered divisons on a scale
weigh
determine the weight of an object, in everyday use the word ‘weighing’ usually means quoting the result as the equivalent mass: ‘my weight is 60 kg’ actually means I have the weight of a 60 kg mass (about 590 N)
peer review
evaluation of scientific work by experts in the same field of study
tension (force)
force that tries to stretch an object or material
compression (force)
force that tries to squash an object or material
deformation
change of shape
normal
perpendicular to a surface
buoyancy force
vertical upwards force on an object placed in or on a fluid, sometimes called upthrust
density
mass/volume
Archimedes’ principle
when an object is wholly or partially immersed in a fluid, it experiences buoyancy force equal to the weight of the fluid displaced
elastic behaviour
a material regains its original shape after a force causing deformation has been removed
elastic limit
the maximum force and/or extension that a material, or spring, can sustain before it becomes permanently deformed
extension
displacement of the end of an object that is being stretched
spring constant, k
the constant seen in Hooke’s law that represents the stiffness of a spring (or other material)
restoring force
force acting in the opposite direction to displacement, returning an object to its equilibrium position
interpolate
estimate a value within a known data range
extrapolate
predict behaviour that is outside of the range of available data
friction
resistive forces opposing relative motion, occurs between solid surfaces, but also with fluids; static friction prevents movement, whereas dynamic friction occurs when there is already motion
coefficient of friction, μ
constants used to represent the amount of friction between two different surfaces, maybe static or dynamic
constant
a number which is assumed to have the same numerical value under a specified range of circumstances
fundamental constants
numbers which are assumed to have exactly the same numerical values under all circumstances and all times
coefficient
a multiplying constant placed before a variable, indicating a physical property
viscosity
resistance of a fluid to movement
viscous drag
the drag force acting on a moving object due to the viscosity of the fluid through which it is moving
turbulence
flow of a fluid which is erratic and unpredictable
Stoke’s law
equation for the viscous drag acting on a smooth, spherical object undergoing non-turbulent motion
streamlined
having a shape that reduces the drag forces acting on an object that is moving through a fluid
field (gravitational, electric or magnetic)
a region of space in which a mass (or a charge, or a current) experiences a force due to the presence of one or more other masses (charges, or currents - moving charges)
free-body diagram
diagram showing all the forces acting on a single object, and no other forces
point particle, mass or charge
theoretical concept used to simplify the discussion of forces acting on objects (especially in gravitational and electric fields)
resultant force
the vector sum of the forces acting on an object, sometimes called the unbalanced or net force
resultant
the single vector that has the same effect as the combination of two or more separate vectors
components (of a vector)
any single vector can be considered as having the same effect as two parts (components) perpendicular to each other
inclined plane
flat surface at an angle to the horizontal (but not perpendicular), a simple device that can be used to reduce the force needed to raise a load; sometimes called a ramp
Newton’s laws of motion
first law: an object will remain at rest, or continue to move in a straight line at a constant speed, unless a resultant force acts on it;
second law: acceleration is proportional to resultant force;
third law: whenever one body exerts a force on another body, the second body exerts exactly the same force on the first body, but in the opposite direction
balanced forces
if an object is in mechanical equilibrium, we describe the forces acting on it as ‘balanced’
equilibrium
an object is in equilibrium if it is unchanging under the action of two or more influences (e.g. forces), different types of equilibrium include translational, rotational and thermal
translational
changing position
natural philosophy
the name used to describe the (philosophical) study of nature and the universe before modern science
proportional relationship
two variables are (directly) proportional to each other if they always have the same ratio
uncertainty bars
vertical and horizontal lines drawn through data points on a graph to represent the uncertainties in the two values
inertia
resistance to a change of motion, depends on the mass of the object
momentum (linear), p
mass times velocity, a vector quantity
system
the object(s) being considered (and nothing else), an isolated system describes a system into which matter and energy cannot flow in or out
surroundings
everything apart from the system that is being considered; similar to the ‘environment’
scientific notation
every number is expressed in the following form: a * 10ᵇ, where a is a decimal number larger than 1 and less than 10 and b is an exponent (integer)
signifcant figures (digits)
all the digits used in data to carry meaning, whether they are before or after a decimal point
collision
two (or more) objects coming together and exerting forces on each other for a relatively short time
explosion
term used in physics to describe when two or more masses, which were initially at rest, are propelled apart from each other
collisions
in an elastic collision the total kinetic energy before and after the collision is the same, in any inelastic collision the total kinetic energy is reduced after the collision, if the objects stick together it is described as a totally inelastic collision
macroscopic
can be observed without the need for a microscope
microscopic
describes anything that is too small to be seen with the unaided eye
recoil
when a bullet is fired from a gun (or similar), the gun must gain equal momentum in the opposite direction
propel
provide a force for an intended motion
jet engine
an engine that achieves propulsion by emitting a fast-moving stream of gas or liquid in the opposite direction from the intended motion
rocket engine
similar to a jet engine, but there is no air intake, instead, an oxidant is carried on the vehicle, together with the fuel
impulse
the product of force and the time for which the force acts
centripetal force
the name given to any force which results in motion along a circular path
banked track
a sloping surface to enable faster motion around curves
centripetal acceleration
the constantly changing velocity of any object moving along a circular path is equivalent to an acceleration towards the centre of the circle
radians
unit of measurement of angle, there are 2π radians in 360°
time period, T
the duration of an event which occurs regularly, T = 1/f
frequency, f
the number of repeating events per unit time
hertz, Hz
derived SI unit of measurement of frequency, 1 Hz = one event per second
angular velocity, ω
change of angle/change of time, sometimes called angular speed
derive
explain in detail the origin of an equation
Note 
Flashcard (27)