Nat 5 Physics Dynamics and Space

Nat 5 Physics Dynamics and Space

1. Space

   • A satellite is an object which orbits another object

2. Vectors and Scalars

   • Average speed is the distance per unit time
     • speed= distance /time
   • Instantaneous speed is the average speed of something over a small distance
     • speed=distance/time
   • Scalar Quantities are defined by magnitude (size) only
     • Scalar Quantities include distance, speed, time, mass, energy and volume
   • Vector quantities are defined by magnitude and direction
     • Vector Quantities include displacement, velocity, acceleration, force and weight
   • Distance is a scalar quantity and displacement is a vector
     • Displacement is the distance and the direction
   • ALWAYS add vectors nose to tail
   • Velocity is the speed of something in a particular direction
     • velocity = displacement/ time
   • Acceleration is the change in velocity per unit time
     • Acceleration= final velocity-initial velocity/ time
       • If a car is slowing down the acceleration is negative
   • The area under a speed time graph is the distance and the area under a velocity time graph is the displacment

3. Newtons Laws

   • Force can change the speed, direction or shape of an object
   • Unit of force is Newtons (N)
   • Forces are vector (direction and size)
   • Mass is the amount of matter that an object has and weight is the force that gravity exerts on an object- weight is a force
     • Gravitational field strength is the weight per unit mass
       • weight= mass x gravitational field strength
       • Earth 9.8 N/kg
   • Friction is a resistive force which opposes the motion of an object
     • Friction is a force which acts between two rough surfaces
       • Friction can be decreased by lubricating the surfaces, separating the surfaces and streamlining
       • Friction can be increased by choosing surfaces which cause high friction and increasing surface area and choosing shape to increase air friction
   • Newtons 1st Law - an object in motion stays in motion and an object at rest stays at rest unless acted on by an unbalanced force
     • no force is equivalent to equal forces
       • For a moving object if the forces are balanced then it will move at a constant velocity
       • For an object at rest if the forces are balanced it will not move
   • Newtons 2nd Law- if an unbalanced force acts on an objects then the object will accelerate in the direction of the force
     • The greater the resultant force the greater the acceleration
       • The smaller the mass the greater the accelaration
         • Unbalanced Force= mass x acceleration
   • The acceleration of something falling vertically is always 9.8m/s^2
   • Newtons 3rd Law - For every action there is an equal and opposite reaction
     • Forces occur in pairs. These two forces are always equal in size but opposite in direction
       • If object A exerts a force (the action) on object B then object B will exert an equal and opposite (reaction) force on object A
         • F1=--F2
   • A projectile is an object that has been given a forward motion but which is also pulled dowards by the force of gravity this results in the path being curved
     • Projectile has both horizontal and vertical motion
       • A projectile travels at a constant speed horizintally and a constant acceleration downwards (9.8)