Interactions between objects
- 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.
Newton's Third law (2)
↑ reaction - up thrust from chair (equal)
↓ action - weight of person (equal)
Newton's Third law (3)
↑ reaction - movment (less)
↓ action - gas (more)
Newton's Third law (4)
← reaction - recoil (more)
→ action - bullet (less)
Newton's Third law (5)
↑ reaction - movement (less)
↓ action - jet gas (more)
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
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
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 collision → speed /velocity of car changes to 0
- in a colision → change 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
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 cars → collapse on impact
- extends time for car to stop
Protection:
- cage - area inside the car which remains unchanged in a collision
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
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)
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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