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Physics ATAR U1 > Newton's Laws > Flashcards

Newton's Laws Flashcards

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1
Q

What are Free-Body Diagrams

A

Shows all forces acting on body/object

Used to calculate net force

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2
Q

What is Force

A

Push or pull on an object

Newtons, Vector quantity

Force directly on body = Contact Force

Force acting on body at a distance = Non-Contact Force

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3
Q

What is net force

A

Sum of all forces acting on object

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4
Q

What is Newton’s 1st Law

A

“An object will continue to move with a constant velocity unless external, unbalanced force acts on it”

At rest = Stays at rest, Moving = Continues moving at same magnitude & direction

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5
Q

What is Law of Inertia

A

Object’s tendency to resist a change in motion

Inertia increases as mass increases
- As harder to start moving if stationary

  • Harder to stop moving if moving
  • Harder to change direction if moving
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6
Q

What is Newton’s 2nd Law

A

“An external force applied, object’s motion will change either magnitude/direction and acceleration of object directly proportional to net force on object, inversely proportional to mass of an object”

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7
Q

What is the Force Due to Gravity Dependent on

A

Larger mass = Larger force due to gravity (Weight)

Mass is directly proportional to gravitational force

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8
Q

What is the Acceleration of Object Dependent on

A

Net Force acting on object, which is directly proportional to acceleration

Mass of object, which is inversely proportional to acceleration

So Net Force = Mass * Acceleration

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9
Q

What is Newton’s Third Law

A

“For every action there is an equal and opposite reaction”

Forces always in pairs, where the force pair acts on different objects, and can never be added together

Objects A & B interact, they exert forces on each other

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10
Q

What is Normal Force

A

Force that counteracts acceleration due to gravity

Not a pair of forces in Newton’s Third Law, as acts on same object

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11
Q

What is weight

A

Force due to something’s mass acting on an object

Vector quantity, Symbol W

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12
Q

What is mass

A

Amount of matter in an object
Not affected by environment

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13
Q

What is Relationship Between Mass and Inertia

A

Greater mass = Greater force needed to accelerate = Greater inertia

Therefore mass directly proportional to inertia

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14
Q

What is Apparent Weight

A

Reaction force due to acceleration due to gravity acting on an object

Force that counteracts gravity

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15
Q

What is Experience of Weight

A

Object beneath you accelerating up = Apparent weight increased, gravity feels stronger

Object beneath you accelerating down = Apparent weight decreased, gravity feels weaker

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16
Q

What is Momentum

A

The product of an object’s mass and velocity

If object moving, it has momentum
Vector quantity

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17
Q

What is Momentum Dependent On

A

How much stuff moving (Mass)

How fast stuff moving (Velocity)

Therefore momentum = mass * velocity

18
Q

What is Conservation of Momentum

A

If no external force acting on system, sum of momentum of objects in system before collision in given direction = Sum of momentum of objects in system after collision in given direction

Therefore Sum of momentum before = Sum of momentum after

19
Q

What Does Seatbelt Do in Motorcycle Safety

A

Newton’s First Law

Seatbelts lock in severe deceleration, opposing the passenger’s motion

  • Is the unbalanced force that acts on the person to decelerate it

Decreases risk of fatality by 50%

20
Q

What Does Safety Barriers Do in Motorcycle Safety

A

Stop out-of-control vehicles from running off-road, or travelling into path of other traffic

Newton’s First Law, where it is the unbalanced force that creates a change in motion, significantly decelerating the car to a stop in little time

Newton’s Second Law, where the force needs to be large, as a car weighs a lot and is moving fast, so has a large net force

The barrier withstands large forces, allowing it to provide a normal force back to the vehicles to stop their motion, is very damaging to vehicle, but prevents widespread harm

21
Q

What Does Airbag Do In Motorcycle Safety

A

Inflates within few ms of collision

Newton’s First Law, where the driver continues to move towards dashboard due to inertia, the driver continues into airbag, where the airbag starts deflating to ensure that the body slows down over longer time, increasing contact time between head and dashboard

Increased time means less force applied for the same change in momentum to driver

22
Q

What Does Helmet Do In Motorcycle Safety

A

Spreads energy of collision over greater area

Newton’s First Law, where motorist will continue moving after crash due to inertia, where the driver will fly off the motorcycle

The outer layer is made from crushable foam, which increases contact time between head and the ground, this increased time means less force applied for same change in momentum to driver

23
Q

What Do Crumple Zones Do In Motorcycle Safety

A

Large distance between driver and front of vehicle

Newton’s First Law, where the cars will continue moving towards eachother due to inertia until fully stopped due to unbalanced forces

The large distance increases time period of which the crash takes place, where this increased time means less force applied for same change in momentum to driver

24
Q

What is Energy

A

The ability to do work

Symbol E, Joules

25
Q

What is Conservation of Energy

A

“Energy cannot be created or destroyed, it can only be transferred or transformed”

Transfer: Transfer energy from 1 object to another
Transform: Transform energy from one type to another

Generally, when Potential Energy decreases = Kinetic Energy increases

26
Q

What is Power

A

The rate at which work is done

Force applied to object to keep it moving over time

27
Q

What is Potential Energy

A

Position of objects relative to one another

28
Q

What is Gravitational Potential Energy

A

Energy due to position above ground / height

Work done against gravitational field

Calculated relative to zero Ep reference level, where point is kept consistent throughout

29
Q

What is Kinetic Energy

A

Energy due to motion

Work done = Change in Kinetic Energy

If object is moving, it has Kinetic Energy

30
Q

What Happens to Kinetic Energy During Inelastic Collisions

A

Kinetic Energy not conserved, converted to waste forms

31
Q

What Happens to Kinetic Energy During Elastic Collisions

A

Kinetic Energy conserved, no waste energy

Kinetic Energy before = Kinetic Energy after

32
Q

What is Mechanical Energy

A

Sum of Potential Energy and Kinetic Energy

33
Q

What is Instantaneous Kinetic Energy or Potential Energy

A

How much kinetic energy or potential energy an object has at certain point in time

34
Q

How is Mechanical Energy Lost

A

When transferred to waste forms (Heat, Sound, Etc.)

Still Kinetic Energy, but not the motion Kinetic Energy

35
Q

What is Efficiency

A

Measure of amount of useful energy we get out of a transfer or transformation

36
Q

What Energies Do Moving Objects Have

A

Moving objects have both Potential Energy and Kinetic Energy

37
Q

What is Work

A

The energy change in object

Done when force causes the object to be displaced, where energy is transferred or transformed

If positive = Energy gained
If negative = Energy lost

38
Q

What is Relationship of Friction and Work

A

No friction = All work transformed to Kinetic Energy, box has higher velocity than before

Some Friction = Some work done transformed to sound/head, the rest Kinetic Energy

A lot of Friction = Box moves at constant velocity, Kinetic Energy doesn’t change as all work becomes heat/sound (Waste)

Therefore changing displacement of body dependent on overcoming friction

39
Q

How To Calculate Work & Displacement At Angle

A

Find horizontal component of force, as this contributes to work

40
Q
A

Physics ATAR U1 (6 decks)

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