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Physics > T5- forces > Flashcards

T5- forces Flashcards

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1
Q

What does it mean if a force does work?

A

The force causes an object to be displaced through a distance along the line of action of the farce

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2
Q

why does air resistance slow down a projectile?

A

The object does work against air resistance. Kinetic energy is converted into heat, slowing down the object.

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3
Q

Explain the relationship between force applied and extension of an elastic object.

A

extension is directly proportional to force applied, provided that the limit of proportionality isn’t exceeded

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4
Q

What is inelastic deformation?

A

The doject is permarenty stretched - doesnt return to its original shape

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5
Q

what is a moment?

A

The turning effect of a force in an anticlockwise or clockwise direction

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6
Q

What distance measurement is used when calculating a moment?

A

The perpendicular from the pivot to the line of action the force.

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7
Q

If an object is in equilibrium what can be said about the moments acting on the object?

A

Clockwise moments = anticlockwise moments

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8
Q

What 3 parts make up a lever system?

A

load, effort, pivot

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9
Q

How can a lever be used as a force multiplier?

A

allow a larger force to act on the load than is supplied by the effort, so it is easier to move heavy objects.
longer lever + the further the effort acts from the pivot= greater force on load

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10
Q

What happens to density of atmosphere with increasing altitude?

A

Atmosphere becomes less dense

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11
Q

Explain why atmospheric pressure decreases with increasing height

A

Pressure is created by collisions of air molecules. The quantity of molecules decreases as height increases.

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12
Q

how does pressure in fluids increase with depth?

A

As depth increases, mass of the liquid above that depth increases.
pressure increases due to weight of fluid

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13
Q

Why does pressure in fluids increase with density?

A

number of particles in the volume increases
Weight of fluid is greater
Force increased so pressure increases.

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14
Q

state the equation which shows the magnitude of pressure in liquids at different depths

A

Pressue due to column of liquid= column height x density x gravitational
field strength
p=hρg

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15
Q

Why are objects in fluids subject to upthust?

A

they have a higher pressure below than above
This creates a resultant force upwards

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16
Q

what is upthrust equal to?

A

The weight of the fluid that the object displaces.

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17
Q

What factors influence whether an object will float or sink?

A

Upthrust, weight, density of fluid.

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18
Q

Why can an object travelling at constant speed not have constant velocity?

A

Speed = scalar quantity
Velocity = vector quantity
so it can only be constant if the direction is constant.
in a circular motion, direction is constantly changing

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19
Q

How can speed be calculated from a distance-time graph?

A

speed= gradient

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20
Q

How do you calculate speed at a given time from a distance-time graph for an accelerating object?

A

Draw a tangent to the curve at the required time. calculate the gradient of the tangent

21
Q

what is a vector quantity?

A

a quantity with a direction and magnitude

22
Q

what is a scalar quantity?

A

a quantity with a magnitude

23
Q

How can a vector quantity be drawn + what does it show?

A

As an arrow
Length = magnitude. Points in direction.

24
Q

3 contact forces

A

Friction, air resistance, tension.

25
Q

3 non contact forces

A

Gravitational, electrostatic, magnetic

26
Q

is force vector or scalar?

A

Vector - it has Magnitude and direction

27
Q

3 vector quantities

A

Velocity, displacement, force

28
Q

3 scalar quantities

A

time, Speed, distance

29
Q

what does weight depend on?

A

gravitational field strength at the given position in the field

30
Q

What is the objects centre of Mass?

A

The point where an objects mass is concentrated.

31
Q

What piece of equipment can be used to measure weight?

A

a calibrated spring balance or newton metre

32
Q

what is a resultant force

A

a single force that is equal to 2 or More forces acting on an object.

33
Q

what is distance

A

how far an object moves
a scalar quantity

34
Q

what is displacement

A

a vector quantity

35
Q

what is speed

A

how fast an object is travelling

36
Q

what is velocity

A

the speed of an object in a direction

37
Q

what happens to the velocity when an object is travelling in a straight line

A

it has constant speed, so it also has constant velocity

38
Q

what happens to the velocity when an object isn’t travelling in a straight line at constant speed

A

although it has constant speed its direction is changing so the velocity changes

39
Q

what happens to the velocity of an object moving in a circle

A

it constantly changes direction so the velocity is constantly changing

40
Q

what is newtons first law

A

an object will remain in its same state of motion until it is acted on by a resultant force

41
Q

what is inertia

A

the tendency for objects to continue in the same state of motion

42
Q

what happens to a stationary object when the resultant force=0

A

it stays stationary

43
Q

what happens to a moving object when the resultant force=0?

A

it moves in the same direction and same speed

44
Q

what do distance time graphs represent

A

the motion of an object travelling in a straight line

45
Q

how do you find the speed of an object from a distance time graph

A

the gradient
speed at a particular time is found by drawing a tangent

46
Q

what is newtons second law

A

the acceleration of an object is directly proportional to the RF acting on the object, but inversely proportional to the mass of the object

47
Q

what is acceleration

A

how quickly an object speeds up/ slows down/ changes direction

48
Q

what happens when an object falls through a fluid

A

the object accelerates due to the force of gravity
as the object speeds up the resistive forces balance the force of gravity
the object falls at terminal velocity

Physics (6 decks)

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