F= m x a
Types of Forces:
- Gravity or weight always acting straight down
- Reaction force from a surface acting straight up
- Electrostatic force between 2 charged objects direction depends on type of charge
- Thrust or Push or Pull speeding something up
- drag or Air resistance or Friction slow things down
- Lift aeroplane wing
- Tension rope or cable
Scalar quantity: only magnitude. an example is speed
Vector quantity: has a magnitude (size) and direction. An example is velocity
Friction is a force that opposes motion
Mass, Weight and Gravity
Weight = Mass x Gravitational Field Strength
W=m x g
Terminal velocity is the constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is failing prevents further acceleration
Sycamore Seeds are an example of terminal velocity
Factors that affect vehicles:
Thinking distance
Stopping distance
Braking distance
Road conditions
Reaction time
Alcohol and drugs
Speed
Mass
Momentum= Mass x Velocity
p= m x v
Momentum and safety:
Seat belts, air bags and crumble zones increase the time taken for the change in the occupants' bodies (during a car crash) which then reduces the forces and chance of injury.
Seat belts- stretch slightly, increasing the time taken and reducing the forces
Air bags- slow you down gradually
Crumble zones- crumble on impact and increasing the time of it to stop
Force acting (N)= Change in momentum (kg m/s) / time taken for change to happen(s)
Moment (Nm) = Force (N) x perpendicular Distance (m) between line of action and pivot
If an object is balanced:
Total clockwise moments = Total anti-clockwise moment
Newton's Third Law
The harder you push, the faster the object will speed up
Paper Two in Bold Italics
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