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IGCSE Physics > 03 Forces And Motion > Flashcards

03 Forces And Motion Flashcards

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1
Q

Distance time graphs: straight line

A

Straight line - represents constant speed

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2
Q

Distance time graphs: the slope of the straight line

A

The slope of the straight line represents the magnitude of the speed

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3
Q

Distance time graphs: a steep slope

A

A slope slope represents large speed
Object is covering more distance per time

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4
Q

Distance time graphs: a shallow slope

A

A shallow slope means the object is moving at a small speed

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5
Q

Distance time graphs: flat horizontal line

A

A flat horizontal line menas the object is stationary (not moving)

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6
Q

Distance time graphs: changing speed

A

Represented by a curve
- if the slope is increasing the speed is increasing (accelerating) object accelerated from starting position
- if the slope is decreasing the speed is decrease (decelerating)

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7
Q

Distance time graphs: calculating speed

A

Gradient of a line
Change in y / change in x

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8
Q

Average speed equation

A

Average speed = distance moved/time taken

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9
Q

Practical: investigate the motion of everyday objects like a tennis ball

A

Independent variable = distance -> use tape measure
Dependent variable = time -> use stopwatch

  • measure a height using tape measure
  • drop tennis bal, which is the distance moved by object
  • use stop watch to measure how long it takes
  • repeat and take avg
  • use equation s=d/t

Errors - human reaction time 0.25 (use data logger), measurements taken at eye level, use light gate to measure time

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10
Q

Acceleration equation

A

Change in velocity/time taken

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11
Q

Unit for acceleration

A

M/s^2

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12
Q

Velocity time graphs: an increasing slope

A

An increasing slope(positive gradient) shows increasing velocity
Object is accelerating

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13
Q

Velocity time graphs: decreasing slope

A

A decreasing slope (negative gradient) represents decreasing velocity
Object is decelerating

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14
Q

Velocity time graphs: straight line

A

A straight line represents constant acceleration/velocity

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15
Q

Velocity time graphs: slope of a line

A

A slope of the line represents the magnitude of acceleration
Steep slope - large acceleration, object speed changes very quickly
Gentle slope - small acceleration, object speed changes very gradually

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16
Q

Velocity time graphs: calculating speed (acceleration)

A

Calculate gradient
Change in y / change in x

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17
Q

Velocity time graphs: finding the distance

A

D = v x t
For triangles 1/2 x b x h

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18
Q

What quantity is force

A

Vector - both direction and magnitude

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19
Q

Vector quantity

A

Has both direction and magnitude (size)

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20
Q

Scalar quantity

A

Has magnitude only

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21
Q

Describe the magnitude and direction of two arrows pointing in opposite directions

A
  • same magnitude (size)
  • heads show its going in opposite directions so the vectors are acting in the opposite direction
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22
Q

Final speed equation

A

(Final speed)^2 = (initial speed)^2 + (2 + acceleration + distance)

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23
Q

Friction is a force that

A

Opposes motion

24
Q

If an object has a 50N force acting north and a 50N force acting south what is the resultant force

A

50N - 50N = 0N

25
Q

Scalar quantities examples

A

Distance, speed, time, mass, temp, pressure , KE, GPE, work done, power, current, resistance

26
Q

Vector quantities

A

Displacement, velocity, acceleration, force, weight, momentum

27
Q

Normal reaction force

A

When an object rests on a solid it feels a reaction force at 90 degrees to surface

28
Q

Gravitation force

A

Also known as weight

29
Q

Drag and air resistance

A

Always acts in opposite direction to motion
Increases if speed increases
Particles of air collide with the object moving through it and slows it motion

30
Q

Friction

A

Acts in the opposite direction to motion

31
Q

Thrust

A

Reaction force
Occurs when mass is pushed out the back of something, causing it to move forward
E.g. rockets, letting go of a balloon, jet engine

32
Q

Upthrust

A

Can only occur in fluids, reason things float
The more fluid the object displaces the greater the upthrust

33
Q

Electrostatic force

A

Force between unlike charges

34
Q

Tension

A

When a pull force is exerted on each end, tension acts across the length of the objects

35
Q

Force equation

A

Mass x acceleration

36
Q

Weight equation

A

Mass x gravitational field strength

37
Q

Stopping distance

A

The total distance travelled during the time it takes to stop in an emergency

38
Q

Stopping distance formula

A

Stopping distance = thinking distance + braking distance

39
Q

Main factors affecting a vehicles stopping distance

A
  • speed (brakes need to do more work to being vehicle to stop)
  • mass (the more mass the more distance it will travel as it comes to a stop)
  • road conditions (wet or icy roads makes brakes less effective)
  • reaction times (increases thinking distance)
40
Q

Thinking distance and its main factors

A

Thinking distance is the distance travelled in the time it takes the driver to react to an emergency and prepare a stop
Main factors: speed of car, reaction time of driver (human avg reaction time is 0.25)

41
Q

Reaction time is increased by

A
  • tiredness
  • distractions (e.g. using a mobile phone)
  • intoxication (e.g. consumption of alcohol or drugs)
42
Q

Describe forces acting on falling object and explain why they reach terminal velocity

A
  • initially thrust/weight is much higher than drag
  • so the car/person accelerates
  • as velocity increases drag increases
  • as drag increases the resultant force (thrust minus drag) overall decreases (f=ma)
  • so acceleration decreases
  • when drag = thrust/weight the resultant force is 0
  • so the car/person travels at constant velocity
  • this is terminal velocity (final velocity the car can reach)
43
Q

Velocity equation

A

Velocity = distance / time

44
Q

Practical: investigate how extension varies with applied force for helical springs, metal wires and rubber bands (force and extension)

A
  • measure the spring/band with no mass added with a ruler and record this initial length
  • add 100 g mass to the hanger of the spring/band
  • record the mass and extension of spring/band
  • add another 100 g
  • record new mass and extension
  • repeat until all masses have been added
  • remove masses and repeat again 3x
  • use equation w = M x g
  • plot graph with
45
Q

Errors of force and extension practical

A
  • wait a few seconds for the spring to fully extend
  • take measurements of the ruler at eye level to avoid parallax error
  • make sure spring doesn’t go past its limit of proportionality otherwise it stretches too far (no longer obeys Hookes law)
46
Q

Hookes law

A

The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality

47
Q

Hookes law: if the force doubles..

A

.. extension will double

48
Q

Hookes law: if the force halves

A

.. extension also halves

49
Q

Limit of proportionality

A

The point where the relationship between force and extension is no longer directly proportional to

50
Q

Which part of a force-extension graph is associated with Hookes law

A

The initial linear region

51
Q

Elastic behaviour

A

Ability of a material to recover its original shape after the forces causing the deformation have been removed
Deformation is a change in the original shape of an object

52
Q

Elastic deformation

A

When the object does return to its original shape after deforming forces are removed
- not permanent
E.g. rubber bands, fabrics, steel springs

53
Q

Inelastic deformation

A

The object does not return to its original shape after deforming forces are removed
- permanent
E.g. plastic, clay, glass

54
Q

Directionally proportional

A

Linear and passes through (0,0)

55
Q

What happens at limit of proportionality

A

Changes in shape are permanent and can’t return to (0,0) as we pass elastic limit
Linear to non-linear

56
Q

What doesn’t obey Hookes law and why

A

Rubber bands -> non linear

57
Q

What doesn’t obey Hookes law and why

A

Rubber bands -> non linear

IGCSE Physics (15 decks)

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