# Shared Flashcard Set

## Details

G481 Mechanics The equations
All the equations you need with definitions and units for OCR A Physics examination
19
Physics
05/14/2009

Term
 Define the symbols, units of measurement and limitations of the equation   Fx = F Cos θ Fy = F Sin θ
Definition
 F is the original force measured in N Fx is the component of F in the horizontal direction Fy is the component of F in the vertical direction θ is the angle between the force vector F and the horizontal.
Term
 Define the symbols, units of measurement and limitations of the equation   a=Δv/Δt
Definition
 a is acceleration measured in ms-2 Δv is the change in velocity and is measured in ms-1 Δt is the change in time measured in seconds
Term
 Define the symbols, units of measurement and limitations of the equation   v = u + at
Definition
 v is the final velocity measured in ms-1 u is the initial velocity measured in ms-1 a is the constant acceleration in ms-2 t is the time taken measured in seconds This equation only works if the acceleration is constant
Term
 Define the symbols, units of measurement and limitations of the equation   s = 0.5(u + v)t
Definition
 s is the distance moved in the direction of the acceleration measued in metres v is the final velocity measured in ms-1 u is the initial velocity measured in ms-1 t is the time taken measured in seconds The acceleration must be constant for this equation to work
Term
 Define the symbols, units of measurement and limitations of the equation   v2 = u2 + 2as
Definition
 s is the distance moved in the direction of the acceleration measued in metres v is the final velocity measured in ms-1 u is the initial velocity measured in ms-1 a is the constant acceleration The acceleration must be constant for this equation to work
Term
 Define the symbols, units of measurement and limitations of the equation   F = ma
Definition
 F is the resultant force (in Newtons) acting on an object of mass, m. (measured in kg) which causes the object to accelerate (measured in ms-2)  If the object is moving very fast then the object mass will increase (relativistic effect) making this equation not work.
Term
 Define the symbols, units of measurement and limitations of the equation   W = mg
Definition
 W is the weight of an object measured in N m is the mass of the object measured in kg g is the gravitational field strength measured in ms-2 or Nkg-1
Term
 Define the symbols, units of measurement and limitations of the equation   Moment = Fx
Definition
 Moment is the turning effect of a force (F measured in N) on a pivotted object x is the perpendicular distance between the force and the pivot
Term
 Define the symbols, units of measurement and limitations of the equation   Torque
Definition
 Two equal but opposite forces (both F) act an equal distance (d/2) from the pivot, one either side[image]of the pivot produce a torque
Term
 Define the symbols, units of measurement and limitations of the equation   ρ = m/V
Definition
 The density (ρ) of a material measured in kgm-3 is the mass (m) in kilograms divided by the volume (V) the mass occupies in m3.
Term
 Define the symbols, units of measurement and limitations of the equation   P = F/A
Definition
 P is the pressure acting on a surface measured in Nm-2 or Pa. (1 Pa = 1 Nm-2) due to a force ,F, measured in N acting on a surface area, A, measured in m2.
Term
 Define the symbols, units of measurement and limitations of the equation   W = FxCosθ
Definition
 W is the work done in Joules when a force, F, measured in N pushes an object a distance x. The angle θ is the angle between the force and the direction moved
Term
 Define the symbols, units of measurement and limitations of the equation   Ek = 0.5mv2
Definition
 The kinetic energy of an object measured in joules is half the product of the objects mass,m, (measured in kg) and velocity in ms-1 squared. If the object is moving very fast then the mass of the object will increase and the equation will not work.
Term
 Define the symbols, units of measurement and limitations of the equation   Ep = mgh
Definition
 The graviational potential energy, Ep, measured in Joules of an object is the product of its mass,m, (measured in kg), its height above the Earths surface,h, in metres and the grsavitational field strength,g, measured in Nkg-1 or ms-2.
Term
 Define the symbols, units of measurement and limitations of the equation   F= kx
Definition
 A force, F, measured in Newtons will cause an extension, x, (in metres) in a wire or spring of stiffness/force constant/spring constant, k, measured in Nm-1. This equation only works for elastic springs and wires
Term
 Define the symbols, units of measurement and limitations of the equation   E = 0.5Fx = 0.5kx2
Definition
 Energy stored (measured in Joules) in a material under tension or compression, F,  (measured in Newtons) x is the the extension of the material in metres and k is the force constant/spring constant/hooke's constant measured in Nm-1 These equations only work for elastic materials
Term
 Define the symbols, units of measurement and limitations of the equation   stress = F/A
Definition
 Stress is measured in Nm-2 Force acting through the material in Newtons A is the cross sectional area of the material measured in m2.
Term
 Define the symbols, units of measurement and limitations of the equation   Strain = x/L
Definition
 Strain describes the change in shape of a material as a fraction x is the extension of the material in metres L is the original length of the material measured in metres.
Term
 Define the symbols, units of measurement and limitations of the equation   Young Modulus = stress/strain
Definition
 Youngs modulus describes the stiffness of a material in Nm-2. Stress is the force ating perunit area through a material measured in Nm-2. Strain describes how the shape of the ibject changes and has no units.   This equation only works for elastic materials
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