Further Mechanics (Unit 4)

Question 1

Newton’s 1st Law

Answer 1

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

Question 2

Newton’s 2nd Law

Answer 2

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

Question 3

Newton’s 3rd Law

Answer 3

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

Question 4

Force (in terms of momentum change)

Answer 4

Force = rate of change of momentum. VECTOR

Question 5

Units of momentum

Answer 5

kgms-1

Question 6

Units of rate of change of momentum

Answer 6

kgms-2

Question 7

Impulse, I

Answer 7

Force x time for which the force acts (F(delta)t)

Hence Impulse = change of momentum. VECTOR

Question 8

Units of Impulse, I

Answer 8

Ns or kgms-1

Question 9

Area under a graph of force against time

Answer 9

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

Question 10

Principle of conservation of linear momentum definition

Answer 10

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

Question 11

Elastic collision definition

Answer 11

A collision where kinetic energy is conserved

Question 12

Inelastic collision definition

Answer 12

A collision where kinetic energy is not conserved.

Note: Total Energy is still conserved.

Question 13

Angular speed, w

Answer 13

angle turned through per second. SCALAR

Question 14

Units of angular speed, w

Answer 14

rad s-1

Question 15

Centripetal force

Answer 15

Resultant force acting towards the centre of the circular path

Question 16

Conditions for shm (simple harmonic motion)

Answer 16

1. acceleration is proportional to displacement

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

Question 17

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

Answer 17

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.

Question 18

Graph of acceleration against displacement.

Answer 18

Gradient = -(2(Pi)f)2

Question 19

Gradient of displacement against time

Answer 19

Gradient of a displacement against time graph is velocity

Question 20

Graphical representations linking x, v, a and t

Answer 20

Check Sheet

Question 21

Conditions for the time period equation of a pendulum

Answer 21

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

Question 22

Dependence of time period on amplitude of an oscillation

Answer 22

Time period of oscillation in SHM is independent of amplitude.

Question 23

Variation of Ep and Ek with displacement

Answer 23

Check Sheet

Question 24

Variation of Ep and Ek with time

Answer 24

Check Sheet

Question 25

Resonance definition

Answer 25

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

Question 26

Free oscillation definition

Answer 26

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

Question 27

Forced oscillation definition

Answer 27

oscillation due to external periodic driving force

Question 28

Time Period

Answer 28

time taken for one complete oscillation

Question 29

Frequency

Answer 29

number of oscillations per second

Question 30

Amplitude

Answer 30

maximum displacement of a particle from its rest position

Question 31

Damping definition

Answer 31

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

Question 32

Damping descriptions

Answer 32

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.

Question 33

Phase difference between driver and driven oscillations

Answer 33

Check Sheet

Question 34

Resonance curve

Answer 34

Check Sheet