Interactions between objects

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  • Created by: Katy **
  • Created on: 03-01-14 15:48

Newton's third law (1)

  • This is when the action = the reaction.
  • This is when the action is opposite to the reaction.
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Newton's Third law (2)

 ↑ reaction - up thrust from chair (equal)

↓ action - weight of person (equal)

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Newton's Third law (3)

↑ reaction - movment (less)

↓ action - gas (more)

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Newton's Third law (4)

 reaction - recoil (more)

→ action - bullet (less)

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Newton's Third law (5)

↑ reaction - movement (less)

↓ action - jet gas (more)

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Energy & Energy transfer

Energy Conservation:

  • energy is not created / destroyed only transferred.
  • heat is created & lost into the environment (dissapated).

Work done:

  • = applied force x distance
  • applied force can be resistance / friction

Kinetic Energy:

  • = mass x (velocity)2

Gravitational Potential Energy (energy due to the change in height):

  • = mass x gravity x change in height
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Energy Changes

Lifting ↑:

  • Work done-

= force x distance

= weight (mass x gravity) x height


Falling:

  • Gravitational potential energy (orginal) -

= mass x gravity x change in height

  • Gravitational potential energy (lost in fall) -

= mass x gravity x change in height - gained kinetic energy

  • Gravitational potential energy lost = gained kinetic energy


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Car Safety (1)

Killing speeds:

  • increasing car speed = bigger chance of being killed

Speed Restrictions:

  • speed  cameras - white lines & 2 cameras
  • speed bumbs
  • road width restrictions

Safety:

  • in a collisionspeed /velocity of car changes to 0
  • in a colisionchange of momentum (mass x velocity before - mass x velocity after)
  • greater inital velocity before impact = greater momentum change
  • greater inital velocity before impact = greater impact force
  • slower velocity before impact = less damage
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Car Safety (2)

Safety Devices:

Force = result of inital velocity/time for car to stop

  • greater time = smaller impact

Seat belts & Air bags:

  • extend time before person (brain) stops
  • seat belts - stretch
  • air bags - soft surface

Crumple Zone:

  • front of modern carscollapse on impact
  • extends time for car to stop

Protection:

  • cage - area inside the car which remains unchanged in a collision


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Car Safety (3)

Stopping distance:

  • Thinking distance is increased by - car speed
  • Thinking distance is affected by driver -

♦tired

♦drugs

♦alcohol

♦distractions

♦radio

♦sat nav

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Car Safety (4)

Braking distance is increased by -

  • car's kinetic energy
  • mass


Braking distance is affected by the car -

  • warm tyres
  • brakes
  • suspention


Braking distance is affected by the road-

  • surface (wet / ice / broken)


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Car Safety (5)

Thinking distance:

= speed (of car) x time (thinking)

  • greater speed = greater thinking distance
  • longer thinking time = greater thinking distance

Braking distance:

  • inital kinetic energy of car = (brake) force x (braking) distance
  • brakes convert kinetic energy of car → heat
  • brake force = friction of tyres / brakes / brake pods
  • smaller brake force = longer brake distance
  • greater mass = longer braking distance
  • greater speed = longer braking distance

speed x2 = braking distance x4

kinetic energy = brake force x braking distance

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