Further Mechanics (Unit 4) Flashcards Preview

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Flashcards in Further Mechanics (Unit 4) Deck (34):
1

Newton’s 1st Law

An object remains at rest or in uniform motion unless acted on by a force

2

Newton’s 2nd Law

The rate of change of momentum of an object is proportional to the resultant force on it

3

Newton’s 3rd Law

When two objects interact they exert equal and opposite forces on each other

4

Force (in terms of momentum change)

Force = rate of change of momentum. VECTOR

5

Units of momentum

kgms-1

6

Units of rate of change of momentum

kgms-2

7

Impulse, I

Force x time for which the force acts (F(delta)t)
Hence Impulse = change of momentum. VECTOR

8

Units of Impulse, I

Ns or kgms-1

9

Area under a graph of force against time

change in momentum ((delta)p) or Impulse I

10

Principle of conservation of linear momentum definition

In a collision (or explosion) the total momentum before equals the total momentum after, providing no external forces are acting.

11

Elastic collision definition

A collision where kinetic energy is conserved

12

Inelastic collision definition

A collision where kinetic energy is not conserved.
Note: Total Energy is still conserved.

13

Angular speed, w

angle turned through per second. SCALAR

14

Units of angular speed, w

rad s-1

15

Centripetal force

Resultant force acting towards the centre of the circular path

16

Conditions for shm (simple harmonic motion)

1. acceleration is proportional to displacement
2. acceleration is in opposite direction to displacement OR acceleration always acts towards the equilibrium position.

17

Relating a= -(2(Pi)f)2 x, to definition of shm

1. acceleration is proportional to displacement
a directly proportional to x and hence a = kx, where k is a constant (2(Pi)f)2.
2. acceleration is in opposite direction to displacement
minus sign indicates that acceleration, a, is in opposite direction to displacement, x.

18

Graph of acceleration against displacement.

Gradient = -(2(Pi)f)2

19

Gradient of displacement against time

Gradient of a displacement against time graph is velocity

20

Graphical representations linking x, v, a and t

Check Sheet

21

Conditions for the time period equation of a pendulum

Time Period equation for a pendulum is only true for oscillations with a small amplitude, that is, angular displacements less than 10 degrees.

22

Dependence of time period on amplitude of an oscillation

Time period of oscillation in SHM is independent of amplitude.

23

Variation of Ep and Ek with displacement

Check Sheet

24

Variation of Ep and Ek with time

Check Sheet

25

Resonance definition

When the driving frequency equals the natural frequency of an oscillating system, vibrations with large amplitude are produced

26

Free oscillation definition

oscillations with a constant amplitude because there are no frictional forces and hence no energy loss.
(Total energy of oscillating system remains constant).

27

Forced oscillation definition

oscillation due to external periodic driving force

28

Time Period

time taken for one complete oscillation

29

Frequency

number of oscillations per second

30

Amplitude

maximum displacement of a particle from its rest position

31

Damping definition

Damping is when frictional forces oppose motion, dissipating energy
(Total energy of oscillating system decreases)

32

Damping descriptions

Light damping : takes a long time for the amplitude to decrease to zero. System oscillates at natural frequency.
Critical damping : shortest time for amplitude to decrease to zero.
Heavy damping : takes a long time for amplitude to decrease to zero. No oscillating motion occurs.

33

Phase difference between driver and driven oscillations

Check Sheet

34

Resonance curve

Check Sheet