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31 Cards in this Set
- Front
- Back
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THINKING DISTANCE
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The distance travelled (by the car) from when the
driver sees a problem and the brakes are applied |
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STOPPING DISTANCE
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stopping distance = thinking distance + braking
distance |
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BRAKING DISTANCE
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The distance travelled by the car after the brakes are
applied until the car stops |
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WORK DONE
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work (done) = force X distance moved in the
direction of force |
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COUPLE (OF FORCES)
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A pair of equal and opposite forces (with their
lines of action separated by a distance) |
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FACTORS AFFECTING BRAKING DISTANCE
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Any two factors from:
speed, mass, condition of tyres, condition of brakes, condition of road, gradient of road For each factor, correct description of how braking distance is affected E.g: • Greater speed means greater distance Or distance ∝ speed^2 • Greater mass means greater distance Or distance ∝ mass • Worn tyres / brakes implies less friction therefore greater distance • Wet / slippery / icy road means less friction therefore greater distance • Uphill means shorter distance Mass of car (1/2 mv^2=Fx, hence braking distance ∝ mass) Speed / Velocity of car (1/2 mv^2=Fx, hence braking distance ∝ speed^2) |
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SAFETY FEATURES ABOUT AIR BAGS
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Large deceleration / rapid decrease in speed
(triggers the air bag) Prevent collision with steering wheel / windscreen / dashboard Time (for stopping) is more / distance (for stopping) is more Smaller deceleration / acceleration (of person) |
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VECTOR QUANTITY
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A quantity that has (both) magnitude / size and
direction |
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SCALAR QUANTITY
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A quantity that has only magnitude and no direction
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TORQUE OF A COUPLE
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torque of a couple = one of forces × perpendicular
distance (between forces) |
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NEWTON
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(Force is 1 N ) when a 1 kg mass has an
acceleration of 1 m s^-2 |
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PLASTIC DEFORMATION
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Material does not return to original length when the force / stress is removed
OR ‘material is permanently deformed’ |
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DETERMINING THE CENTRE OF GRAVITY OF AN OBJECT
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1. (Suspend plate from a point and then) mark a
vertical line on the plate (wtte) 2. Plumb line / ‘pendulum’ (used to find the vertical line) 3. Hang from another point / place (and draw another vertical line) (wtte) 4. Where the lines intersect gives position of centre of gravity (wtte) |
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GPS
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1. (Several) satellites used
2. Distance from (each) satellite is determined 3. Position / distance is determined using c / speed of e.m waves / radio waves / microwaves and delay time 4. Trilateration is used to locate the position of the car Or position of car is where circles / spheres cross Time taken for the signal to travel from satellite to car is determined / ‘delay’ time for signal is determined distance = c (delay) time |
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PRINCIPLE OF CONSERVATION OF ENERGY
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total energy of a (closed) system remains
constant or Energy cannot be created or destroyed (it can only be transferred into other forms) or total initial energy = total final energy |
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ACCELERATION
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acceleration = rate of change of velocity
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VELOCITY
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velocity = rate of change of displacement
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MOMENT OF A FORCE
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moment = force X perpendicular distance from
pivot |
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CENTRE OF GRAVITY
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The point where the weight (appears) to act
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HOOKE'S LAW
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Extension is proportional to force (applied
as long as the elastic limit is not exceeded) |
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YOUNG MODULUS
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Young modulus = stress/strain
As long as the elastic limit is not exceeded / in the linear region of stress against strain graph / Hooke’s law is obeyed |
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GALILEO/ARISTOTLE EXPERIMENT
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Galileo dropped different mass balls / rolled different mass
balls (down a ramp) Balls hit the ground / reached the bottom (of ramp) at the same time (Galileo -) All objects fall with the same acceleration and (Aristotle -) Heavy / massive objects fall faster / quicker (than light objects) |
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SAFETY FEATURES ABOUT SEAT BELTS
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Increases time (of impact / to slow down) / increases
the distance (travelled by the driver) Smaller deceleration / acceleration Force is smaller because F= ma and acceleration is smaller or force is smaller because F = Ek/x and x is bigger or force is smaller because F=∆p/∆t and ∆t is bigger |
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CONDITIONS FOR AN OBJECT TO BE IN EQUILIBRIUM
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Net force = 0
Net moment / torque = 0 |
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POWER
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power = work done/ time
or energy/time or ‘rate of work done’ |
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PROPERTIES OF SOME MATERIALS
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BRITTLE MATERIAL
No plastic deformation / It is elastic / It returns to same length when stress / force is removed It breaks when reaches elastic limit POLYMERIC MATERIAL It is elastic / It returns to same length when stress / force is removed |
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FACTORS AFFECTING DRAG WHEN AN OBJECT IS FALLING THROUGH AIR
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area
speed / velocity viscosity (of air) / temperature / density |
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DETERMINING FREE FALL
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Measurements:
height (of wall) time (of fall) Instruments: ruler / tape (measure) stopwatch / timer / clock /video (APPROPRIATE FORMULAE) Any two from: g is an estimate because air resistance / drag ignored parallax problems with ‘landing time’ starting / stopping the clock |
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DENSITY
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density = mass/volume or ‘density is mass per
(unit) volume’ |
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PRINCIPLE OF MOMENTS
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(When an object is in equilibrium the) sum of clockwise
moments (about a point) = sum of anticlockwise moments (about the same point) |
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PARACHUTES
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When the parachute is opened, drag increases / drag is
greater than the weight Drag decreases as the speed decreases / net force decreases The (magnitude of the) deceleration decreases deceleration or acceleration = 0 |
