Forces & Motion

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  • Forces & Motion
    • Distance and Velocity Time Graphs
      • Distance Time Graphs
        • Calculating speed from graph
          • Speed=gradient= vertical/horizontal
        • 1) Gradient= Speed
          • Flats shows stopped
            • Steeper part is faster
              • curves show acceleration or deacceleration
                • curve starting to level off means slowing down
      • Velocity Time Graphs
        • Calculating acceleration from a velocity time graph
          • Acceleration= gradient= vertical/ horizontal=Answer
    • Terminal Velocity
      • Free- Fallers reach terminal Velocity
        • 1.When free falling objects first set off, they have much more force accelerating then resistance slowing them down.
        • 2.As the velocity, increase it builds resistance slowing them down
        • 3. The acceleration gradually slows down until both acceleration and resistance forces are equal. This is terminal velocity
    • Newtons Three Laws of Motion
      • First Law
        • Law: Balanced forces mean no change in velocity
        • As long as all the forces are balanced it stays still
      • Second Law
        • Law: A resultant Force means acceleration
        • If there is an unbalanced force, then the object will accelerate in that direction
      • Third law
        • If object A exerts a force on object B then object B exerts the exact opposite force on Object A
        • Law: Reaction Forces
      • Resultant Force
        • To work it out use: Force= mass x acceleration
    • Momentum
      • Meaning: Momentum is conserved when no external factors act. The total momentum after is the same as it was before
      • Calculating Momentum use: Momentum= Mass x Velocity
      • Force causes changes in Momentum
        • Formula: Force Acting (N)= Change in Momentum/Time taken for change to happen
    • Acceleration
      • Speed Formula Speed= Distance/  time
        • Only use this formula when speed is constant
      • Calculating Acceleration
        • Formula: Acceleration= change in velocity/ Time Taken
        • Remember: Change in velocity is final velocity minus initial velocity
        • Acceleration is how quickly the velocity is chaging
    • Turning Forces
      • A Moment is the turning effect of a force
        • The force on the spanner causes a turning effect or moment on the nut. A larger force would mean a larger momentum
      • Formula: Moment= Force x perpendicular distance (m) between line of action and pivot
      • The centre of gravity hangs directly below point of suspension
    • Principle of Moments
      • Question of Balance- Are the moments equal
        • The Answer: If an object is balanced then: Total Anticlockwise Moments= Total clockwise moments
      • Forces are not always equal across all support
      • If a light rode is being supported at both ends, the upward force provided by each support, won't be  the same
      • And if the Moments are not equal
        • If the total anticlockwise moments do not equal the total clockwise moments, there will be a resultant moment
    • Hooke`s Law
      • Hooke's Law says that Extension is proportional to force.
      • A metal spring will also obey hooke's Law,  if two opposite forces are applied to each end.
      • Hooke's law stops working when the force is great enough
      • A material can return to its original shape after an elastic deformation expect past hooke's Law
    • Gravity and the Universe
      • Our Solar System is in the Milky Way Galaxy
      • Gravity provides the force that causes orbits
        • It provides orbits which excist in:
          • 1) Any object travelling in a circle is constantly charging direction
            • 2) Any orbit is a balance between forward motion and backward motion
              • 3)The planets move around the sun in almost a circular orbit.
              • 4) Gravity is responsible for all our other planets in our solar system
                • The moon orbits the earth. Other planets also have there own moons.
                • Artificial Satellites that are made by man and launched into space.
                • Comets are small lumps of icy rock orbiting the earth
      • The Universe is a large collection of billions of Galaxies
    • Orbital Speed
      • Gravity decreases as you go further away
      • There are different types of orbits:
        • 1) Orbits of moons and planets
        • 2)Comets orbit with very elliptical orbits
        • 3)Comets have much longer than earth as it has to travel the outer edge of the solar system
        • 4) Some artificial earth satellites have an orbital period of exactly one day
      • Working out the speed of an Orbiting Object
        • Step 1: Calculate the speed of an orbit using: Speed= Distance/time
          • Step 2:For a circular orbit, the distance travelled is the circumference of the orbit, which to calculate distance= 2 x pie x radius of orbit
            • Step 3- So the formula for speed of an orbit is: Orbital speed= (2 x pie x obital radius) / time period
    • Vectors
      • There are loads of different types of force
        • Gravity and Weight
        • Reaction Force
        • Electrostatic Force
        • Thrust
        • Drag
        • Lift
      • Friction is always their to slow things down

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