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Forces Flashcards

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1
Q

What are scalar quantities?

A

Only have one magnitude and no direction.

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2
Q

What are the examples of scalar quantities?

A 
> speed.
> distance.
> temperature.
> mass.
> time.
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3
Q

What are vector quantities?

A

Have a magnitude and a direction.

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4
Q

What are the examples of vector quantities?

A 
> force.
> displacement.
> momentum.
> velocity.
> acceleration.
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5
Q

What is meant by the term “force” in physics?

A

A push or pull on an object caused by it interacting with something.

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6
Q

What are the two types of forces?

A

> contact forces.

> non-contact forces.

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7
Q

What are contact forces?

A

Where objects have to be touching.

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8
Q

What are non-contact forces?

A

Where objects don’t need to be touching.

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9
Q

What are some examples of contact forces?

A

> friction.
tension.
air resistance.
normal contact force.

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10
Q

What are some examples of non-contact forces?

A

> electrostatic force.
gravitational force.
magnetic force.

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11
Q

What is meant by the term “weight” in physics?

A

Force that acts on an object due to gravity.

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12
Q

What is the formulae for weight?

A

weight = mass x gravitational field strength
w = m g
N kg N/kg

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13
Q

What is the centre of mass?

A

Point at which an object’s weight appears to act.

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14
Q

What is a free body diagram?

A

Shows all forces acting on an isolated object.

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15
Q

What is an equilibrium?

A

When the forces acting on an object are balanced and the resultant force is zero.

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16
Q

What is a resultant force?

A

A single force that can replace all the forces acting on an object to give the same effect as all the original forces acting together.

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17
Q

What are the two ways of calculating resultant force?

A

1)
> add forces pointing in same direction.
> subtract forces pointing in opposite directions.
> F₁ - F₂ = resultant force.

2)
> draw forces to scale and tip-to-tail.
> measure length of resultant force to find its magnitude and angle to find its direction.

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18
Q

What is work done?

A

When a force moves an object from one point to another, energy is transferred and work is done on the object.

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19
Q

What is the formulae for work done?

A

work done = force x distance
w = f x s
J N M

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20
Q

How can a stationary object change its shape?

A

When more than one force act on it.

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21
Q

What are the two types of deformation?

A

> elastic.

> inelastic.

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22
Q

What is the elastic type of deformation?

A

Where an object goes back to its original shape and length after forces have been removed.

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23
Q

What is the inelastic type of deformation?

A

Where an object doesn’t go back to its original shape and length after forces have been removed.

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24
Q

What is the formulae for force?

A

force = spring constant x extension/compression
F = k x e
N N/m m

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25
Q

What is distance?

A

How far an object has moved.
[scalar]
[not including its direction]

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26
Q

What is displacement?

A

The distance and the direction in a straight line from an object’s starting point to its finishing point.
[vector]

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27
Q

What is speed?

A

How fast you’re going with no regard to direction.

[scalar]

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28
Q

What is the formulae for distance travelled?

A

distance travelled = speed x time
s = v x t
m m/s s

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29
Q

What are the factors that can affect a person’s walking, running and cycling speed?

A

> ability.
age.
distance travelled.
type of ground.

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30
Q

What is velocity?

A

The speed in a certain direction.

[vector]

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31
Q

What happens to an objects velocity if they are moving in a circular motion with a constant speed?

A

The velocity changes.

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32
Q

What is acceleration?

A

The change in velocity in a certain amount of time.

33
Q

What is the formulae for acceleration?

A

acceleration = change in velocity ÷ time
a = ∆v ÷ t
m/s² m/s s

34
Q

What is deceleration?

A

Negative acceleration which shows an object is slowing down.

35
Q

What is Newton’s first law?

A

> if zero resultant force acts on stationary object, the object doesn’t move.
if zero resultant force acts on moving object, it continues moving at same velocity.
if non-zero resultant force acts on an object, the object accelerates.

36
Q

What is inertia?

A

The tendency of an object to continue in. the same state of motion.

37
Q

What is Newton’s second law?

A

> acceleration is directly proportional to resultant force.
↳ F ∝ a.
acceleration is inversely proportional to mass.

38
Q

What is the formulae for resultant force?

A

resultant force = mass x acceleration
F = m x a
N kg m/s²

39
Q

What is inertial mass?

A

Measure of how hard it is to change an object’s velocity.

Its the ratio of force over acceleration: m = F ÷ a.

40
Q

What is Newton’s third law?

A

Two interacting objects exert equal and opposite forces on each other.

41
Q

What is an example of Newton’s third law?

A

1)
> rocket exhaust gas pushed downwards by rocket.
↳ causes equal and opposite force as gas pushes back on rocket.
↳rocket moves when upwards than rocket’s weight.

2)
> girl pushes on wall.
↳ equilibrium - wall pushes back on girl with equal and opposite force.

42
Q

What is friction?

A

A force that acts to oppose an object’s motion. It always acts in the opposite direction to movement.

43
Q

What is drag?

A

The frictional force caused by any fluid on a moving object.

[e.g. air resistance]

44
Q

What is the process of reaching terminal velocity?

A

force of gravity greater than frictional force ⟶ object acceleration ⟶ speed increases so friction increases ⟶ frictional force = force of gravity ⟶ resultant force is zero ⟶ terminal velocity reached.

45
Q

What are the three factors that affect reaction times?

A

> tiredness.
drugs.
alcohol.

46
Q

What are the steps to investigate reaction time?

A

> get someone to hold ruler so zero is between your thumb and forefingers.
↳ ruler dropped without warning and caught as fast as possible.
↳ use distance ruler fell to calculate reaction time.

47
Q

What is the formulae to find stopping distance?

A

stopping distance = thinking distance + braking distance

48
Q

What is thinking distance?

A

How far a vehicle moves during driver’s reaction time.

49
Q

What is braking distance?

A

Distance taken to stop whilst brakes are applied.

50
Q

What are the two factors that increase thinking distance?

A

> faster vehicle speed.

> slow driver reaction times.

51
Q

What are the four factors that increase braking distance?

A

> faster vehicle speed.
wet or icy weather.
poor road surface.
damaged or worn brakes or tyres.

52
Q

What is the work done when stopping?

A

> driver brakes causing brake pads to be pressed onto wheels.
↳ friction between them causes work to be done.
↳ energy transferred from kinetic energy stores of wheels to thermal energy stores of brakes.
↳ brakes heat up.

53
Q

What can large deceleration cause?

A

> brakes to overheat.

> vehicle to skid.

54
Q

What is the formulae for momentum?

A

momentum = mass x velocity
p = m x v
kg m/s kg m/s

55
Q

How is momentum affected by mass and velocity?

A

> the greater an object’s mass, the greater its momentum.

> the greater an objects velocity, the greater its momentum.

56
Q

What is the transfer between joule and newton-metre?

A

1 joule = 1 newton-metre.

56
Q

What is the typical value for walking, running and cycling?

A

> walking = 1.5 m/s
running = 3 m/s
cycling = 6 m/s

57
Q

What is the equation for uniform acceleration?

A

(final velocity)² - (initial velocity)² = 2 x acceleration x distance
v² - u² = 2 x a x s
m/s m/s m/s² m

58
Q

What is the formulae to calculate the work done in stretching or compressing a spring?

A

elastic potential energy = 0.5 x spring constant x (extension)²
Eℯ = 1/2 x k x e

59
Q

What state of matter is a fluid?

A

It can either be a liquid or gas.

60
Q

What is the formulae to calculate the pressure at the surface of a fluid?

A

pressure = force normal to a surface / area of that surface
p = F / A
PA N m²

61
Q

What is the formulae to calculate the pressure due to a column of liquid?

A

pressure = height of the column x density of the liquid x gravitational field strength
p = h x 𝛒 x g
PA m kg/m³ N/kg

61
Q

What is the formulae to calculate the pressure due to a column of liquid?

A

pressure = height of the column x density of the liquid x gravitational field strength
p = h x 𝛒 x g
PA m kg/m³ N/kg

62
Q

What is the force called upthrust?

A

When a partially (or totally) submerged object experiences a greater pressure on the bottom surface than on the top surface which creates a resultant force upwards.

63
Q

What is the atmosphere?

A

A thin layer (relative to the size of the Earth) of air round the Earth.

64
Q

What happens to the atmosphere where there is an increasing altitude?

A

It gets less dense.

65
Q

How is atmospheric pressure created?

A

When air molecules collide with a surface.

66
Q

What happens to the atmospheric pressure as there is an increase in height?

A

It decreases.

67
Q

Why does the atmospheric pressure decrease with an increase in height?

A

The number of air molecules above a surface decreases as the height of the surface above ground level increases. So as height increases there is always less air above a surface than there is at a lower height.

68
Q

What happens when force is applied to the brakes of a vehicle?

A

Work is done by friction force between the brakes and the wheel reduces the kinetic energy of the vehicle increasing the temperature of the brakes.

69
Q

The greater the speed of a vehicle…

A

…the greater the breaking force needed to stop the vehicle in a certain distance.

70
Q

The greater the braking force…

A

…the greater the deceleration of the vehicle.

71
Q

Why are large decelerations dangerous?

A

It may lead to brakes overheating and/or loss of control.

72
Q

What is the conservation of momentum?

A

When in a closed system, the total momentum before an event is equal to the total momentum after the event.

73
Q

Why are cars designed to slow people down over a longer time when they have a crash?

A

The longer it takes for a change in momentum, the smaller the rate of change of momentum and so the smaller the force.

74
Q

Why are seat belts used as a safety feature?

A

They stretch slightly increasing the time taken for the wearer to stop.

75
Q

Why are air bags used as a safety feature?

A

They inflate before you hit the dashboard of a car. The compressing air inside slows you down more gradually.

76
Q

Why are gymnasium crash mats/cushioned playground flooring used as a safety feature?

A

They increase the time taken for you to stop if you fall on them.

77
Q

Why are cycle helmets used as a safety feature?

A

They contain a crushable layer of foam which helps to lengthen the time taken for your head to stop in a crash reducing the impact on your brain.

physics. (10 decks)

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