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Flashcards in Mod 5 Advanced Mechanics Deck (23)
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1

What is non-unifrom circular motion

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

2

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) 

3

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

  • Centripetal force 
  • Tangential force

4

Is net force constant in unifrom circular motion

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

5

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

6

What 2 equations are equated to find orbital velocity

  • F = mv^2/r
  • F = GMm/r^2

7

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

8

How do you prove that projectile motion is parabolic

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

9

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

10

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

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

11

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

12

How is energy required to transfer to a new orbit calculated

  • W = E(orbit)f-E(orbit)i

13

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)

14

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

15

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)

16

What is Kepler's second law

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

17

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

0

18

How is weightlessness calculated

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

19

What is coefficient of friction

muN

20

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

21

What is centripetal force acting on a rigid body

  • F = mv^2/ r = mrw^2

22

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

23