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gsce physics > forces and motion 1 > Flashcards

forces and motion 1 Flashcards

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1
Q

what is a scalar & an example of it?

A

has only magnitude:
speed
distance

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2
Q

what is a vector & what’s an example of one?

A

magnitude and direction:
velocity
displacement
force

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3
Q

equation for speed?

A

speed = distance / time

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4
Q

equation for velocity?

A

velocity = displacement(distance) / time

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5
Q

what is speed measured in?

A

m/s

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6
Q

what is acceleration?

A

the rate of change in velocity

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7
Q

what is the equation for acceleration?

A

acceleration = change in velocity / time

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8
Q

what’s on the y axis and x axis of a distance time graph?

A

y - distance
x - time

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9
Q

what does the gradient of the line in a distance time graph tell you?

A

the speed

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10
Q

what does a / line suggest in a distance time graph?

A

constant speed

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11
Q

what does a - line tell us in a distance time graph?

A

stationary

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12
Q

how do you find the gradient of a curved line?

A

draw a tangent to the line

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13
Q

what’s on the y and x axis of a velocity time graph?

A

y - velocity
x - time

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14
Q

what does the gradient of a velocity time graph tell us?

A

acceleration

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15
Q

what does / mean in a velocity time graph?

A

constant positive acceleration

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16
Q

what does a - line mean in a velocity time graph?

A

velocity is constant

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17
Q

how do you find the distance travelled in a velocity time graph?

A

find area under the curve

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18
Q

what’s the first law of motion (newton)?

A

a resultant force is required to change the motion of an object

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19
Q

what is (newtons) second law of motion?

A

if a resultant force acts on an object it will cause the object to accelerate

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20
Q

newton’s second law
the size of the resultant force is…

A

directly proportional to the acceleration it causes

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21
Q

what is the equation for force?

A

force (N) = mass(kg) x acceleration(m/s2)

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22
Q

what is acceleration messaged in?

A

m/s^2

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23
Q

what is force messaged in?

A

N newtons

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24
Q

what’s newton’s third law?

A

when two objects interact the forces they exert on each other are equal (magnitude) and opposite (direction)

if you are pushing a box -> 100N however the box will push back <- 100N (normal contact force)

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25
Q

all forces are..

A

vectors

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26
Q

what is the resultant force?

A

the overall force on an object

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27
Q

what is it called when an object has no resultant force?

A

equilibrium

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28
Q

what is terminal velocity?

A

when velocity remains constant

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29
Q

what are two things that affect air resistance?

A

surface area - the greater the surface area the greater number of collisions of air particles
velocity - the faster they are moving the more particles they will collide with

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30
Q

what do you call it when an object has changed shape?

A

deformed

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31
Q

what is it called when an object returns to its original shape after force has been applied?

A

elastic

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32
Q

what do you call it when an object stays deformed?

A

inelastic

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33
Q

what is extension?

A

the increase in length of a spring when it’s stretched

34
Q

what is force proportional to?

A

force is proportional to extension

35
Q

what is it called when force and extension are directly proportional?

A

hookes law

36
Q

what is stopping distance?

A

minimum distance required to stop a vehicle in an emergency

37
Q

what’s the equation for stopping distance?

A

stopping distance = thinking distance + braking distance

38
Q

what is thinking distance?

A

how far the car travels during the driver’s reaction time
driver seeing hazard and applying the break

39
Q

what are two things that affect thinking distance?

A

speed
-faster the further you travel
reaction time
-tired
-drunk
-drugs etc all increase reaction time

40
Q

what is braking distance?

A

distance taken to stop under the braking force

41
Q

what are some factors affecting braking distance?

A

speed
mass
-both increasing kinetic energy that needs to be 0 to stop
condition or quality of brakes
-if worn or faulty it won’t slow car as quick so car will travel further
traction between the car and road
-wet
-icy
tire conditions

42
Q

what forces act on falling object?

A

weight
air resistance

43
Q

what’s the equation linking mass, gravitational field strength, weight?

A

weight = mass x gravitational field strength

44
Q

what is weight measured in?

A

N
newtons

45
Q

what is the force that is push or pull?

A

applied force

46
Q

what is the force in which masses are attracted to each other and the centre of the earth (weight)?

A

gravitational force

47
Q

what is a force that acts in opposite directions?

A

friction

48
Q

what is the force that causes drag?

A

air resistance or drag

49
Q

what is the force that requires a stretch or compress?

A

spring force

50
Q

what force happens in springs or cables when they are stretched?

A

tension

51
Q

what is the force called that occurs when mass is pushed out the back of something so causing the object to move forward?

A

thrust

52
Q

what type of force of thrust only occurs in fluids?

A

up-thrust
reason things float

53
Q

what is the force that causes upward movement?

A

lift

54
Q

what is the force that an attraction pulls two opposite poles together and visa versa?

A

magnetic

55
Q

what is the force of attraction that pulls two opposite charges together?

A

electrostatic

56
Q

where does the weight of a body act through?

A

centre of gravity

57
Q

how can you measure the speed of a object at the bottom of the ramp?

A
  • place a marker at the bottom of ramp
  • measure a distance or 20cm from marker
  • place the object at top of ramp and release
  • using the marker measure the time it takes for the marker to move to the 20cm marker
  • repeat this three times releasing marbles from the same position each time
  • average time
  • use equation speed = distance / time
  • by varying the height of ramp to see how height affects the speed of the marble at the bottom
58
Q

how can you measure the speed of an object while it’s going down a ramp?

A
  • feed the ticker tape through the timer
  • place the object at starting point
  • attach the ticker tape to object
  • start the ticker tape timer and carefully release the object (do not push)
  • stop object when it reaches bottom of ramp
  • remove ticker timer to analyse and repeat
59
Q

how does a ticker tape timer work?

A

prints 50 dots per second on tape
if dots are far away object has covered more distance per time and travelled fast

60
Q

how does a light gate work?

A

vehicle must have an interrupter to break beam of light
measures how long it takes for interrupter to pass
for example, if it takes 0.2 secs and interrupter is 10cm long you do 10cm/02s to find speed

61
Q

how do you work out the gradient of distance / time graph?

A

gradient = rise / run

62
Q

how do you work out final speed?

A

(final speed)^2 = (initial speed)^2 +(2 x acceleration x distance moved)

63
Q

what’s normal reaction force?

A

when an object rests or is in contact with a solid surface, 90 degree reaction force to surface

64
Q

what opposes motion?

A

friction

65
Q

what is surface friction?

A

occurs between two surfaces than are in contact
- can stop an object from moving
- can oppose an object sliding
- can oppose an object rolling

66
Q

what is air resistance?

A

opposition force of an object moving through gas (air) and drag is often used for the opposition of an object through a liquid
- reduce air resistance and drag by making an object more streamlined
- both increase with increasing speed

67
Q

what would the weight of an 80kg person on the moon be?

A

on earth: 80kg x 10N/kg = 800N
on moon: 80kg x 1.6N/kg = 128N

moon gfs is 1/6 of earths

68
Q

describe the forces that act on a falling object and what happens?

A
  • initially no air resistance and only force acting on its weight
  • as it falls it accelerates which increases its speed and hence air resistance
  • causes the resultant force downwards to decreases
  • acceleration decreases so not speeding up as quickly
  • eventually they are equal and opposite and balance so there is no resultant force
  • no acceleration and the terminal velocity is reached
69
Q

practical: investigate how extension varies with applied forces for helical springs, metal wires and rubber bands

A
  • set up your apparatus as shown in the
  • measure the length of your spring without
    any hanging masses.
  • hang a mass of 100g on the spring
  • measure the new length of the spring
  • calculate the extension of the spring
  • repeat steps 3-5 for increasing the mass
    in increments of 100g
  • take note of your results in the table

hookes law region is where force is directly proportional to extension - elastic
limit to proportionality X
curved - inelastic
spring breaks

70
Q

what’s on the x axis of a spring/ weight graph?

A

spring displacement cm

71
Q

what’s on the y axis of a spring/ weight graph?

A

weight

72
Q

what is elastic behaviour?

A

is the ability of a material to recover original shape after the force is removed
in a spring this occurs when the force is lower than the elastic limit
loading and unloading force extension curves can be different as long as it returns to its original shape

73
Q

how do you work out momentum?

A

momentum = mass x velocity

74
Q

how do you create safety features linking momentum?

A

to reduce the force experienced by the passenger you need to extend the time for a passenger to stop in a collision
as force is the change in momentum divided by time
to reduce force experienced by the passengers you need to extend the time taken for a passenger to stop in a collision
MOMENTUM= MASS X VELOCITY (DISPLACEMENT/TIME)
FORCE= CHANGE IN MOMENTUM/TIME

75
Q

what’s the conservation of momentum of object?

A

momentum before the collision = momentum after the collision
so,
momentum A before the collision + momentum B before the collision = momentum A & B after the collision moving together

76
Q

what’s the relationship between force, change in momentum and time taken?

A

force = change in momentum / time taken

77
Q

what’s newton’s third law?

A

when two objects interact, they apply forces to each other of equal magnitude and opposite direction

78
Q

what’s the relationship of moment, force, perpendicular distance from pivot?

A

moment = force x perpendicular distance from the pivot

79
Q

where does the weight of a body act through?

A

centre of gravity

80
Q

use the principle of moments for a simple system of parallel forces acting in one plane:

A

principle of moments states that when the clockwise moments are equal to the anticlockwise moments a body will be in equilibrium

clockwise moments = anticlockwise moments

81
Q

how does the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam?

A

when moments are taken from the right hand side as the block is a greater distance the force from the left hand pivot must be bigger to counteract it.
the opposite is true for the left hand side

82
Q

what’s momentum measured in?

A

Kg m/s

gsce physics (9 decks)

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