2.2 Dynamics

• A forces can:

  • change the shape of an object
  • change the speed of an object
  • change the direction of travel of an object
• The size of a force is measured by a newton balance in Newtons (N)
• Mass is the quantity of matter in an object, measured in kilograms.
• Weight is a force which is caused by the pull of gravity on an object and is measured in Newtons (N)
• Gravitational field strength is defined as the weight per unit mass
• W=mg

  w=weight (N)

  m= mass (kg)

  g= gravitational field strength (N/kg)
• Friction is a force that opposes motion between two surfaces that are in contact with each other.
• Friction is a resistive force which always acts in the opposite direction to the movement.
• Air resistance is caused when an object moves through the air and collides with air particle.
• Factors affecting air resistance are :

  • shape and size of the moving object
  • speed of moving object
• Balanced forces are equal but in opposite directions so the resultant unbalanced force is 0N
• Newtons first law: An object will remain at rest or in motion unless acted upon by an unbalanced force
• Newtons second law:when an object is acted on by a constant unbalanced force the body moves with a constant acceleration in the direction of the unbalanced force.
• • The greater an unbalanced force the greater the acceleration
  • The smaller the mass the greater the acceleration
• When an object is in free fall the weight of the object will be balanced by the air resistance and then fall at a constant velocity.This final velocity is called terminal velocity
• Fun=ma

  Fun= unbalanced force (N)

  m = mass (Kg)

  a = acceleration (ms-2)
• Newtons pairs of forces
• Newtons 3rd law: For every action there is an equal and opposite reaction
• The path of a projectile is curved due to the horizontal and vertical velocities.
• To calculate

  vertical velocity: v=u+at

  horizontal velocity: v=d/t
• Apparent weightlessness is when objects (e.g in space) are constantly accelerating towards the earth due to gravity.