Interpreting graphs of motion
Gradient of the graph is velocity.
Gradient of the graph is acceleration.
Area under the graph is displacement.
Area under the graph is velocity.
Speed- Distance/Time = ms-1
Acceleration- Change in velocity/Time = ms-2
Force- Mass X Acceleration= Newton. Kgms-2
Pressure- Force/Area = pascal (Pa). Kgm-1s-2
Work- Force X Distance = Jouke. Kgm2s-2
Power- Work/ Time = Watt . Kgm2s-3
Equations of motion
The 3 equations of motion are:
v = u + at
v2 = u2 + 2as
s = ut + 1/2at2
v = final velocity
u = initial velocity
a = acceleration
t = time
s = displacement
Elastic deformation: will return to original dimensions when force is removed
Plastic: will remain deformed
Hard: Difficult to indent
Stiff: high young modulus
Tough: high energy density/ large plastic region/ able to absorb energy
Brittle: an object will shatter when subject to shocks, without deforming plastically.
Strong: high breaking stress/ can withstand large forces before it breaks
Malleable: hammered into thin sheets
Ductile: Can be drawn into wires without losing their strength
Stress, Strain, Young Modulus etc
Hookes Law= up to a given load, the extension of a pring is directly proportional to the force applied to the spring. F= KX (k-spring constant)
Limit of proportionality- the point the material stops obeying hooks law. but would still return to its original shape if stress is removed.
Elastic limit- at this point the material starts to behave plastically. at this point the material would no longer return to its original shape once the stress was removed.
Yield point- the stress at which a large amont of plastic deformation takes place with a constant or reduced load.
Work done= 1/2 X Max force X extention
Elastic strain energy= the area under the graph.
Stress=Force/Cross sectional area
Strain=Extension/ original length
Young modulus= stress/strain.
Tensile strain and stress
Tensile strength: The tensile stress at which a material fails.
Tensile force: The tensile force required to stretch a material.
Tensile stress: The tensile force per unit cross-secitonal area.
Tensile strain: The extension per unit length.
Strength: A materials ability to withstand stress.
Stiffness: A material which resists tensile force.
Upthrust= a consequence of water pressre being greater below an immersed obect
Upthrust= weight displaced = vpg
an object willfloat in a fluid if the upthrust is equal to its weight
laminar flow=no abrupt change in velocity or direction of flow lines. adjacent layersdo not cross over each other
turbulent= streamlines are no longer continuous
viscosity= the resistance of a fluid to flow
Resultant force= W-(U+F) If an object is accelerating downwards
viscous drag increases untill (u+f)= w << terminal velocity.