Unit 1 Physics. Edexcel

Key points to remember for unit 1 physics AS  exam.

• Created by: megan
• Created on: 16-05-12 19:34

Scalar or Vector?

Scalar Quantities=

• distance
• speed
• time
• mass
• volume
• temperature

Vector Quantities=

• displacement
• velocity
• acceleration
• force
• weight
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Units

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

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Forces

Newtons first law= an object will remain in a state of rest or continue to move with a constant velocity unless acted up by a resultant external force

Newtons second law= the acceleration of a body of constant mass is proportional to  the resultant force applied to it and in the direction of the resultant force F=MA

Newtons third law= if body A exerts a force on body B. body b will exert an equal and opposite force on body a. third law paris mst: act on 2 seperate bodies, same type, same line, equal magnitude, opposite directions.

Work done=force X distance moved. (joules)

mgh= gpe

power = work done/time taken.  (watts)

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Motion

Average Velocity= Displacement/Time

Any change in velocty= Accerating. The magnitude of acceleration is a measure of the rate at which velocity changes.

Acceleration= Change in velocity/ Change in time.

in the absence of air resistance,all objects fall with acceleration- 9.81 ms-2

neglecting air resistance, the horizontal component of the initial velocity will remain constant.

Instantaneous velocity is the gradient of the graph at a point. Can be measure by drawing a tangent on the line.

Velocity time graphs- gradient= acceleration.deceleration= a negative gradient. Area under graph= displacement.

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Materials

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

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Materials (2)

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.

Energy density= work done/ volume = 1/2 X stress X strain = the area under a stress stain graph.

the hysteresis loop for a stress starin graph represents the energy per unit volume transferred to internal energy during the cycle.

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Fluids.

Density=  Mass/Volume

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.

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