Our Dynamic Universe delete

• Resultant force


  A single force which has the same effect on an object as multiple forces
• Vector


  Quantity with both magnitude and direction
• Scaler

  Quantity with magnitude only
• Vector examples

  Displacement

  Force

  Weight

  Velocity

  Acceleration
• Scaler examples

  Distance

  Energy

  Mass

  Speed

  Time

  Temperature
• Area under velocity/time graph


  Displacement
• Gradient of velocity/time graph

  Acceleration
• Area under displacement/time graph

  Nothing
• Gradient of displacement/time graph


  Velocity
• Vertical component of vector (Vv)

  xsin0
• Horizontal component of vector (Vh)


  xcos0
• Projectile


  Any object, which once projected, continues its motion by its own inertia and is influenced only by the downward force of gravity
• Horizontal component of projectile


  No forces acting so horizontal velocity is constant
• Vertical component of projectile

  Force due to gravity is constant so constant vertical acceleration
• Path of projectile is symmetrical across horizontal plane so...

  Initial vertical velocity = -final vertical velocity

  Time of flight = 2x time to highest point

  Vertical velocity at highest point is zero
• Horizontal direction of motion in projectile


  Air resistance negligible so no forces

  Constant velocity

  No acceleration
• Vertical direction of motion in projectile

  Air resistance negligible so only force due to gravity

  Velocity changing at constant rate

  Constant acceleration of 9.8ms-²
• Terminal velocity

  The velocity of a falling object when the weight of the object (force acting downwards) is balanced by a frictional force acting upwards on the object (since these forces are balanced the object will fall witj a constant velocity)
• Projectile motion


  An object will follow a curved path due to:

  - a constant horizontal velocity

  - a vertical acceleration due to the force of gravity
• Satellite orbit


  A satellite stays in orbit because it is falling towards the earth's surface at the same rate as the earth's surface is curving away from the satellite
• Low orbit satellites


  -Period of approximately 90 minutes

  -used for weather monitoring and mapping

  Eg. ISS LEO
• Geostationary satellite


  -Satellite which stays above the same point on the earth's surface at all times

  -period of 24 hours

  Height of 36000km above earth's surface

  -provide consistent communication across the globe

  -used for telecommunications and television
• Newton's first law

  An object at rest will remain at rest unless acted upon by any unbalanced force. An object in motion will remain in motion with the same speed and direction unless acted upon by am unbalanced force
• Newton's second law

  When an unbalanced force acts on an object it causes it to accelerate in the direction of the unbalanced force. This acceleration is directly proportional to the unbalanced force and inversely proportional to the mass.

  Fun=ma
• Newton's third law


  For every action force there is an equal but opposite reaction force
• Tension


  Between two boxes
• Weight


  Force due to gravity on the object
• Gravitational field strength

  Force due to gravity per unit mass (1kg)
• Rocket just after take off

  There is an unbalanced force upwards due to large force of thrust, the rocket accelerates upwards
• As the rocket rises


  Mass is lost as fuel is used up. Therefore the weight of the rocket decreases. The unbalanced force upwards increases, therefore acceleration increases.
• Top of lift

  -lighter than normal weight

  -reading on scales<weight

  a=-ve

  Fun=-ve
• Middle of lift


  -normal weight

  -reading on scales =weight

  a=0

  Fun=0
• Reading on scales

  Apparent weight
• Bottom of lift

  -Heavier than normal weight

  -Reading on scales>weight

  a=+ve

  Fun=+ve
• Normal


  Perpendicular to slope
• Down the slope


  Parallel to slope
• Law of conservation of energy

  Energy cannot be created or destroyed, only converted from one form to another
• Work done


  Converting one form of energy to another
• Power


  Measure of the rate at which the energy is converted
• Momentum

  Measure of an object's motion and is the product of mass and velocity