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36 Cards in this Set
- Front
- Back
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Scalars |
Magnitude but no direction (e.g mass/speed) |
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Vectors |
Magnitude and direction (e.g force and velocity) |
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Adding vectors |
If perp pythag/trig If not draw out scale diagram |
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Free body force diagrams |
Show all forces acting on a body but not the forces it exerts |
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Moment (Nm) = |
Force (N) * perp distance (m) |
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For equilibrium... |
Up=down Left=right Sum anticlockwise=sum clockwise |
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Couple |
Pair of coplanar forces acting in parallel with same magnitude in opposite directions resulting in a turning force |
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Couple moment= |
Force of one * distance between them |
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Inertia |
Resistance to change in velocity > mass = > inertia |
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Mass and weight |
Mass scalar Weight vector Weight = mg |
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Centre of mass |
Single pt on object where you can consider it's entire weight to act through Object will always balance around this pt |
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Finding com |
By symmetry (regular object) where los cross By experiment (hang object from a pt draw vertical line using plumb Bob, do from diff pt) Where lines cross = com |
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Stability |
Depends on com and base area If vertical line down from com falls outside base area object topples Low com, large base area = > stable |
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SUVAT equations |
V=U+AT (NO S) S=VT-0.5AT^2 (NO U) S=UT+0.5AT^2 (NO V) S=0.5(U+V)T (NO A) V^2=U^2+2AS (NO T) |
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Free fall |
Objects in free fall accelerate at same rate Only force acting is weight |
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DT and vt using ict |
Data logger (e.g ultrasound position detector) attached to computer with graph drawing software |
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SUVAT |
V=u+at S=ut+0.5at^2 V^2=u^2+2as S=0.5(u+v)t |
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Finding g experiment |
Disconnect electromagnet n start timer Ball hits trapdoor breaks circuit stops timer Do at diff heights Draw graph h by t^2 Gradient =0.5g Use small heavy ball for small air resistance Biggest error is ruler uncertainty |
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Free fall |
Only weight acting All objects in free fall accelerate at same rate (9.81ms^-2) |
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Projectile motion |
If projected at an angle resolve into initial horizontal and vertical velocities and do seperate suvat |
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Newton's 1st law |
A force is needed to change velocity If forces aren't balanced Fr will cause body to accelerate |
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Newton's 2nd law |
Acceleration proportional to force F=kA F=ma |
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Galileo (falling) |
All objects fall at same rate w/ no AR F=ma mg=ma g=a regardless of mass |
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Newton's 3rd law |
Every force has an equal opposite reaction force (forces always same type e.g gravitational) |
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Newton's 3rd law |
Every force has an equal opposite reaction force (forces always same type e.g gravitational) |
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Friction |
Opposes motion Coverts Ek into heat and sound Fr(max)= uR |
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Terminal speed |
Occurs when driving speed = friction force |
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How to increase vehicles max speed |
Increase driving force (engine size) Decrease friction force (>streamlined) |
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Describe skydiver journey |
Jumps...accelerates, air resistance =0 acceleration=9.81 As speed increases air resistance increases until speed=AR Now travelling at terminal speed Parachute opens AR>weight acceleration slows until reachers TV again |
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Momentum |
=mass*velocity Conserved in all collisions and explosions |
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Elastic and inelastic collisions |
Ek conserved in elastic |
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Impulse |
Change in momentum Ft=mv-mu Ft=change in momentum |
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Impulse |
Change in momentum Ft=mv-mu Ft=change in momentum |
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Car safety features |
Crumple zones (crumples on impact increasing time to stop Seat belts (stretch increasing time for wearer to stop) Air bags (slow down passengers more gradually and prevent from hitting hard surfaces) |
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Work |
Done whenever energy is transfered =force*distance Area under forces displacement graph |
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Power |
Rate of energy transfer F*V F*D/t Energy transfered/second Work done/second |
