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forces Flashcards

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1
Q

what is a scalar quantity?

A

a quantity that only has a magnitude, it is direction dependent

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2
Q

what is a vector?

A

a quantity has both an associated direction and magnitude

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3
Q

How can a vector quality be drawn and what does it show?

A
  • an arrow
  • the arrow points in certain directions
  • the length of the arrow represents the magnitude
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4
Q

what is a force

A

a push or pull acting on an object due to an interaction with another object

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5
Q

what are the two forces categories

A
  1. non-contact forces
  2. contact forces
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6
Q

3 examples of contact forces

A
  1. friction
  2. air resistance
  3. tension
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7
Q

3 examples of non-contact forces

A
  1. gravitational forces
  2. electrostatic forces
  3. magnetic forces
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8
Q

is force a vector or a scalar quantity

A
  • vector
  • it has a magnitude and an associated direction
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9
Q

3 examples of a vector quantity

A
  1. velocity
  2. displacement
  3. force
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10
Q

examples of scalar quantities

A
  1. temp
  2. time
  3. mass
  4. speed
  5. distance
  6. energy
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11
Q

what is weight

A

the force that acts on an object due to gravity and the objects mass

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12
Q

weight equation

A

weight = mass x gravitational field strength

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13
Q

unit for weight

A

Newton (N)

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14
Q

unit for gravitational field strength

A

N/Kg

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15
Q

what is meant by an objects centre of mass

A

the single point where an objects weight can be considered to act through

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16
Q

what is the name given to the single force that is equivalent to all the other forces acting on a given object

A

the resultant force

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17
Q

what is the equation used to calculate work done?

A

work done = force x distance

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18
Q

what distance must be used when calculating work done

A

the distance that is moved along the line of action of the force

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19
Q

what occurs when work is done against frictional forces

A
  • rise in temp
  • kinetic energy is converted to heat energy
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20
Q

explain the relationship between the force applied and the extension of an elastic object

A

the extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded

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21
Q

what is meant by inelastic deformation?

A
  • a deformation which results in an object being permanently stretched
  • the object does not return to its original shape when force is removed
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22
Q

state the equation relating force, spring constant, extension

A

force = spring constant x extension

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23
Q

what type of energy is stored in a spring when its stretched

A

elastic potential energy

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24
Q

what is an alternative name for the turning effect of a force

A

a moment

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25
Q

state the equation to calculate the moment of a force

A

moment of a force = force x distance

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26
Q

what distance measurement is used when calculating a moment

A

the perpendicular distance from the pivot to the line of action of the force

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27
Q

if an object is in equilibrium, what can be said about the moments acting on a force

A

the clockwise moments are equal to the anticlockwise moments

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28
Q

3 parts of lever system

A
  1. load
  2. pivot
  3. effort
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29
Q

how can a lever be used as a force multiplier

A

if the distance between the effort and pivot is greater than the distance between the pivot and load, the force applied on the load is greater than the effort force. this is since the moment on both the effort and the load must be the same

30
Q

example of when a lever may be used to multiply a force

A

a wrench
it has a long handle so that the force applied by the user is multiplied

31
Q

what determines the moment of a gear wheel

A

the size of the wheel

32
Q

describe the moment and speed of a larger gear being driven by a smaller gear

A

the larger wheel will rotate more slowly but will also produce a larger moment

33
Q

does a distance quantity require a specific distance

A

no specific distance is needed
so it is a scalar quantity

34
Q

typical value for speed of sound

A

330 m/s

35
Q

typical value for human walking speed

A

1.5m/s

36
Q

typical value for human running speed

A

3 m/s

37
Q

typical value for human cycling speed

A

6 m/s

38
Q

equation that links speed, distance and time

A

distance = speed x time

39
Q

why can an object travelling at a constant speed in a circle not have a constant velocity

A
  • speed is a scalar quantity
  • velocity is a vector quantity which means it can only be constant if the direction is constant
  • the a circular motion, the direction is constantly moving
40
Q

how can speed by calculated from a distance-time graph

A

the speed is equal to the gradient of the graph

41
Q

what must be done to calculate speed at a given time from a distance-time graph from a accelerating object

A
  • draw a tangent to the curve at the required time
  • calculating gradient of the tangent
42
Q

equation for average acceleration of an object

A

acceleration = change in velocity / time taken

43
Q

how can the distance travelled by an object be calculated from a velocity time graph

A

it is equal the the area under the graph

44
Q

approx value for the acceleration of an object in free fall under gravity (earth surface)

A

9.8 m/s(squared)

45
Q

what can be said about the resultant force acting on an object when it is falling at terminal velocity

A
  • resultant force is zero
  • what at terminal velocity, the object is moving at a constant speed and so isn’t accelerating
46
Q

state newtons first law of motion

A

every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.

47
Q

what can be said out the braking forces and driving forces when a car is travelling at constant velocity

A

the braking forces are equal to the driving forces

48
Q

what is inertia

A

the tendency of an object to continue its state of uniform motion or rest

49
Q

equation for newtons 2nd law of motion

A

resultant force = mass x acceleration

50
Q

newtons 2nd law of motion

A

an objects acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass

51
Q

what is inertia mass

A
  • a measure of how difficult it is to change a given objects velocity
  • the ratio of force over acceleration
52
Q

newtons 3rd law of motion

A

His third law states that for every action (force) in nature there is an equal and opposite reaction.

53
Q

what is the stopping distance of a vehicle equal to

A

sum of thinking distance and braking distance

54
Q

for braking distance:
if the vehicle speed increased what would happen to the stopping distance

A

the stopping distance is increased with an increase in speed

55
Q

3 factors which effect drivers reaction time

A
  1. tiredness
  2. drugs
  3. alcohol
56
Q

2 factors which effect braking distance

A
  1. road conditions
  2. poor tyre brake conditions
57
Q

describe the energy transfers that take place when a car applies its breaks

A
  • work done by the friction between brakes and wheel
  • kinetic energy of wheel is converted to heat and is dissipated to the surroundings through brake discs
58
Q

To stop a car in a given distance if it’s velocity is increased, what must happen to the braking force is applied

A

The braking force must also be increased

59
Q

State 2 consequences of a vehicle undergoing very large decelerations

A
  1. Kinetic energy converted to heat is very high causing brakes to overheat
    2 loss of control of the vehicle
60
Q

equation for pressure

A

pressure = force / area

61
Q

equation for pressure in a fluid column

A

pressure = height of fluid above the point x density x field strength

62
Q

what is meant by fluid

A

a liquid or a gas

63
Q

what happens to the density of the atmosphere with increasing altitude

A

the atmosphere becomes less dense as altitude increases

64
Q

how does pressure in fluids increase with depth

A

as the depth increases, the mass of liquid above that depth also increases. this means that the force due to the mass increases. since the force has increased whilst the area has remained constant, the pressure will increase

65
Q

why does pressure in fluids increase with density

A

as the density of a fluid increases, the number of particles in a given volume increases. consequently the weight of the fluid is greater, the means that the force from the liquid above a certain point is larger. since the force has increased, the pressure also increased

66
Q

why are objects in a fluid subject to an upthrust?

A

when an object is submerged in a fluid, it has a higher pressure below it then it does above, as there is more weight above it at the bottom than there is at the top. this leads to an upwards force called up thrust. you float or sink depending on weather the up thrust is more or less your weight

67
Q

what is upthrust always equal to

A

the weight of the fluid that the object displaces

68
Q

factors that will influence whether an object will sink or float

A
  • upthrust
  • weight
  • density of fluid
69
Q

explain why an object with a density greater than that of water can never float

A

upthrust is equal to the weight of the displaced fluid. if the density of the object is high, there would not be enough volume displaced to produce an upthrust larger than the objects weight. it will sink

70
Q
A

physics (9 decks)

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