Dynamics

• Scalar vs vector

  scalar- a quantity with magnitude only for example distance speed time energy mass

  vector- a quantity with magnitude and direction for example displacement velocity acceleration force
• Resultant of two vectors in one dimension or at right angles has to be nose to tail
• Displacement: the action of moving something from its place or position
• Speed is distance per unit time v=d/t
• Velocity is the displacement travelled over time v=s/t
• Average speed is the distance travelled over time v(bar)=d/t
• Instantaneous speed is the speed of an object at a particular point in time. v(bar)=s/t
• Measuring average speed is done by using a trolley on a ramp with a single mask and two light gates and measuring the distance between both light gates and taking note of the time taken for the trolley to pass through the light gates using a stopwatch
• measuring instantaneous speed is similar to average but only using a single light gate with a double mask and measuring the time taken for the front part to pass with the end of the mask stopping the timer
• Acceleration is the change in velocity per unit time cal by a=v-u/t. To determine the gradient use the same equation
• Experiment to measure acceleration is two light gates connected to a timer with the trolley moving down the ramp and the trolley has a double mask on top, measure width of cards and move trolley down the ramp and timer gives initial speed, final speed and time to then use equation
• To determine displacement of velocity time graph we use s=area under v-t graph
• Newton’s first law is when forces acting on an object are balanced the object will remain the same. Example is if an object is at rest it will continue to remain at rest.
• forces to explain motion

  • force due to gravity
  • friction
  • thrust
  • drag
  • air resistance
  • pull
  • push
  • buoyancy
  • lift
  • tension
• newtons second law states that force = mass x acceleration or F=ma
• Newtons second all is about unbalanced forces. When an object accelerates and is directly proportional to the force acting on it and inversely proportional to the mass of the object. There will be a change in speed shape or direction. Using equation F=ma
• Newton’s third law is about equal but opposite force. That is A exerts force on B then B will exert equal but opposite force to A

  meaning there is always an reaction force
• Weight is caused by the pull of gravity acting on a mass measured in kilograms (kg)
• Free fall is when an object is dropped from a height and it falls freely without air resistance. Eventually the weight due to gravity will become balanced with the air resistance and will fall at a constant rate known as terminal velocity.
• Energy can’t be created or destroyed but transformed from one form to another
• Kinetic energy is energy possessed by virtue of movement. Depends on the mass and velocity of the object.

  Equation is Ek=1/2mv(squared)
• Work done means the potential energy lost=kinetic energy gained
• Work done means the energy transferred
• Projectile motion follows a curved path due to gravity

  Considered as vertical or horizontal
• Horizontal projectiles is measured by v=s/t
• Vertical projectiles is measured by v=u + at that is rearranged from a=v-u/t