Physics

 Force

  • Pull or push
  • measured in Newton
  • First Law/Law of inertia
      • No friction in space -> object will keep on moving unless acted upon
      • A body at rest remains at rest or, if in motion, remains in motion at constant valocity unless acted on by a net external force
  • Second Law
    • acceleration is proportional to Force and inversely  proportional to mass  a = F/m => F=ma
    • When equal force is applied in opp direction -> then object will not move
    • When both kick the ball in same direction -> Force will be sum of two forces
    • a = sigma F/m 
    • Fnet = ma  -> second law of motion
  • Third law
    • Whenever one body exerts a force on a second body, then first body experiences a force that is equal in magnitude and opposite in direction to the force that it excerts. Mathematically, if a body A exerts a force F on body B, then B simultaneously exerts a for -F on A, or in vector equation form.
      For every action, there is an equal and opposite reaction.
    • eg: swimmer pushing legs against wall
  • Weight is not mass
    • weight is force measured in Newton, mass in kg
    • Weight is pull of earth on an object. It depends on the distance from the center of Earth. mass doesn't vary with location
  • Normal force is always perpendicular to the surface of the object it is sitting on
  • Weight always directed to center of earth
  • Freebody diagram
    • Wx = m.g.sin
      Wy = m.g.cos
  • Friction is a force that opposes relative motion between systems in contact
    • it is directed in opp direction of motion
    • Static Friction (fs)- Two systems are in contact and stationary
    • Kinetic friction (fk)- two systems are in contact and moving relative to one another
    • fs <=mu s*m*g, fsmax = mu m.
    • fk <=mu k*m*g, fkmax = muk m.g
    • sum of forces on object is m.a(mass * acceleration)
    • forces on X direction = push force- friction =  P - m*a = 
    • forces on Y direction = Normal force - Weight  will be null
    • max static friction = mu * m *g
  •  Circular motion
    • speed is not constant as direction keeps changing
    •  a = v^2 / r (centripetal accelation)
    • F =  m.a => Fc = m * v^2 / r
  • Central force(Conical Pendulum)
    • F =  m.a => Fc = m * v^2 / r = sin theta
    • Effective force = m.a = T cos theta - m.g = 0( not moving on y direction)
      • T cos theta = m.g
  • Net Force = m * a = force applied - friction


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