Physics P2 Forces and their effects

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  • Forces and their effects
    • Resultant Forces
      • A stationary object remains stationary if the sum of the forces acting on it is zero.
      • If an object has multiple forces acting on it-then the resultant force is ALL forces added together.
      • When forces are balanced then the resultant force is zero and would mean that...
        • A stationary object remains stationary
        • A moving object keeps on moving at the same speed and in the same direction
      • Non-zero resultant forces
        • When the forces are balanced the resultant force is not zero
          • This means that a stationary object accelerates in the direction of the resultant force
        • Effects of a non-resultant force
          • The object was already moving so moves faster than before
          • The object is still but begins to move upwards
          • The bar was de-celerating so de-celerates faster.
      • Force,Mass and acceleration
        • An object will accelerate in the direction of the resultant force. A force on a large mass will accelerate the object less. doubling mass halves mass
        • Acceleration= force/ mass
    • Forces and Motion
      • Distance time graphs
        • When going across the objectis stationary
        • Gradient= speed
        • Speed= distance/time
      • Velocity time graph
        • Velocity is speed in a particular direction
        • Different velocities (eg 2 cars)
          • Different speed in the same direction
          • Same speed but different directions
          • Different speeds in different directions
        • Across the graph is constant velocity
        • gradient= area under graph
      • Acceleration
        • a=(v-u)/t  (a= acceleration, v+ the final velocity, u=starting velocity and t is time)
    • Forces and Braking
      • The stopping distance on a car depends on 2 things- thinking distance and braking distance.
      • When a vehicle is travelling at a steady speed the engines force is balanced by air resistance.
      • Potential forces
        • The driving force- from the engine
        • Reaction force on wheels- moves the car up
        • Friction- between roads and tyres
        • Gravity- downward force
        • Air resistance- slows down the object
      • For something to slow down two things have to occur
        • The resistive forces must be increased
        • The driving force must be reduced
      • Stopping distance= thinking distance + braking distance
      • Thinking distance is the distance for a driver to brake.
        • This could be increased by tiredness, distractions, alcohol , drugs
      • Braking distance is the time taken to stop
        • This could be increased by poor brakes, weather conditions
    • Forces and terminal velocity
      • Falling objects have two main forces acting on them: the weight and air resistance
      • The 3 stages of falling. At the start, the object accelerates downwards due to weight
        • Then air resistance increases
          • Then the objects weight is equalled by air resistance- its terminal velocity
      • Weight is the force acting on an onject- a result on gravity
      • W=m*g
    • Forces and elasticity
      • A force acting on an object can change the shape of an object
      • Hookes law- the length of a spring is directly proportional to the force applied
      • F=k*e (f is force, k is a spring constant and e is extension
      • However, all elastic objects have a different elastic limit


hollie rawlings

thank you for this is was very helpful.

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