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Flashcards in Mod 5 Advanced Mechanics Deck (23)
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What is non-unifrom circular motion

Circular motion where the speed of the object changes as it moves around a fixed path


What cause non-uniform circular motion

The net force is chaging in magnitude and in direction and hence does not provide required centripetal force (radial force) 


What two components form net force in non-uniform circular motion

  • Centripetal force 
  • Tangential force


Is net force constant in unifrom circular motion

Yes, since net force is centripetal force towards centre of circle


When a rocket is launched into a LEO how does its energy change during the journey 

The rockets total mechanical energy (E= U + K) increases since work is done on rocket through use of thrusters to burn fuel


What 2 equations are equated to find orbital velocity

  • F = mv^2/r
  • F = GMm/r^2


Why don't AC induction motors need brushes or slip rings

Current in the squirrel cage rotor is induced through three phase AC power supply not directly supplied


How do you prove that projectile motion is parabolic

  • Through showing that equations of motion are in the form:
  • y = ax^2+bx+c


What is the general process for solving projectile motion questions

  1. What is the value of g (are we on Earth)
  2. Do we have u(y)
  3. No --> find u(y) first
  4. Yes --> Try to solve by analysing vertical motion and use equations of motion
  5. if No find time using s(x) = u(x)t


What are the forces acting on an object on a banked track

  • Normal force to track
  • weight force mg directly down
  • Acceration towards centre


Why are objects able to travel around banked tracks without any sideway force on the wheels by the track

  • The normal force is tilted as a result of the banking
  • Therefore a component of the normal force towards the centre of rotation exists and acts as a centripetal force required to execute a circular motion hence sideway force is not required


How is energy required to transfer to a new orbit calculated

  • W = E(orbit)f-E(orbit)i


How is total mechanical energy of a satellite in orbit calculated

  • E = U + K
  • E = -GMm/r + 1/2(mv^2)
  • E = -GMm/r + 1/2 m(GM/r)
  • E = - 1/2 (GMm/r)


What impact does a chnage in mass of a space probe have on its motion

  • r^3/T^2 = constant
  • independent of mass of orbiting probe
  • Any change in mass will not affect ratio hence if altitude remains the same then orbital period remains the same
  • Speed is given by v = 2(pi)r/T since r and T do not change orbital velocity remains constant


How is escape velocity calculated 

  • When E = U + K = 0
  • Hence 1/2mv^2 - GMm/r = 0
  • 1/2v^2 = GM/r
  • Vesc = sqrt(2GM/r)


What is Kepler's second law

  • Equal time equal areas
  • v(A)/v(B) = r(B)/r(A)


What is total energy of an orbit when v = v(escape)



How is weightlessness calculated

  • When apparent weight = 0
  • or normal force = 0


What is coefficient of friction



What is process for solving uniform circular motion questions

  • Identify forces --> N is perpendicular to object, weight is vertically down, Tension is pulling force along wire, friction is towards centre
  • Determine acceleration acceleration always towards centre
  • Decompose the forces
  • Apply F = ma to find unknowns


What is centripetal force acting on a rigid body

  • F = mv^2/ r = mrw^2


What are the two ways we can take advantage of Earth's rotation to launch satellites into orbits

  • Launch vertically at the equator velocity from axial rotation is greatest
  • Launch towards East tangential velocity from Earths rotation is added