523754
Descrição
FlashCards por nikeishabk, atualizado more than 1 year ago
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Criado por nikeishabk
quase 11 anos atrás
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| Questão | Responda |
| Describe an experiment to determine the acceleration of free fall g using a falling body. | Measurements: Height (distance) Time (of fall) Instruments: Stop watch/timer/clock/video Ruler/tape (measure) Calculation: g = 2s/t2 or g = 2 gradient of . s-t2 graph g is an estimate: air resistance / drag parallax (landing time) starting/stopping the clock ((v+u)/t = s/t, v=u+at, u=0) (s=ut+1/2at^2 (ut=0), s = at^2/2, a(g)=2s/t^2). |
| Describe the motion of bodies falling in a uniform gravitational field with drag. | Acceleration: Terminal velocity: Net / total / resultant force (on drop) is zero ‘upward force = downward force’ / ‘weight = drag’ / ‘weight balances drag’ |
| Describe a simple experiment to determine the centre of gravity of an object. | Suspend object from a point and then) mark a vertical line on the object Plumb line / ‘pendulum’ (used to find the vertical line) Hang from another point / place (and draw another vertical line) (wtte) Where the lines intersect gives position of centre of gravity (wtte). |
| Describe the factors that affect thinking distance and braking distance. | speed, mass, condition of tyres/tread, condition of brakes, condition of road (surface), gradient of road For each factor, correct description of how braking distance is affected : Greater speed means greater distance OR distance ∝ speed2 Greater mass means greater distance OR distance ∝ mass Worn tyres / brakes implies less friction therefore greater distance Bald tyres Wet / slippery / icy road means less friction therefore greater distance Uphill means shorter distance. |
| Describe and explain how air bags, seat belts and crumple zones in cars reduce impact forces in accident. | Prevent collision with steering wheel / windscreen /dashboard Time for stopping is more / distance for stopping is more / seat belt ‘stretches’ Smaller deceleration / acceleration (of person) Reference to K.E.=Fs or ½ mv^2=Fs. |
| Describe how air bags work, including the triggering mechanism. | Large deceleration / rapid decrease in speed (triggers the air bag). |
| Describe how the trilateration technique is used in GPS. | (Several) satellites used Distance from (each) satellite is determined. Time taken for signal to travel from satellite to car/‘delay’ time for signal is determined. Distance = c x ‘delay’ time Position / distance is determined using c / speed of e.m waves / radio waves / microwaves and delay time Trilateration is used to locate the position of the car OR position of car is where circles/spheres cross/intersect. |
| Describe the behaviour of springs and wires in terms of force, extension, elastic limit, Hooke’s law and the force constant (ie force per unit extension or compression). | Measurement: original / initial length (Not: final length) extension / initial and final lengths, weight / mass Equipment: Micrometer / vernier (calliper) (for the diameter of the wire) Ruler / (metre) rule / tape measure (for measuring the original length / extension) Travelling microscope (for measuring extension) Scales / balance (for measuring the mass & mg equation is used or for measuring weight) / Newton meter (for the weight of hanging masses) / ‘known’ weights used. |
| Describe an experiment to determine the Young modulus of a metal in the form of a wire. |
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| Describe the shapes of the stress against strain graphs for typical materials. |
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