6.1 Periodic motion

Question 1

Define Uniform Circular Motion.

Answer 1

When an object is moving in a circular path at a constant speed.

Question 2

What is the resultant force called in this scenario?

Answer 2

Centripetal force

Question 3

What is the equation(s) for centripetal force?

Answer 3

Question 4

What do the letters represent in this equation?

Answer 4

Question 5

What direction does the centripetal force act in?

Answer 5

Towards the centre of the circle

Question 6

Why is the object accelerating when its speed is constant?

Answer 6

Centripetal force acts perpendicular to the direction of motion, and so constantly changes the direction of the velocity vector.

Question 7

Define centripetal acceleration.

Answer 7

Acceleration of an object moving in a circular path.

Question 8

What is the equation(s) for centripetal force?

Answer 8

Question 9

What do the letters represent in this equation?

Answer 9

Question 10

What direction does the centripetal acceleration act in?

Answer 10

Towards the centre of the circle

(Same direction as the centripetal force, since F=ma)

Question 11

Define angular displacement?

Answer 11

The angle an object moves through as it travels along a circular path

(The angle in radians)

Question 12

Define arc length.

Answer 12

The distance an object moves through as it travels along a circular path.

Question 13

What do the letters represent in this equation?

Answer 13

Question 14

Define the radian.

Answer 14

1 radian is when s=r in the arc length equation.

1 radian = 57.3 degrees

Question 15

How can you convert from radians to degrees?

Answer 15

Think of the 180 being in units of degrees and the pi being in units of radians

Question 16

How can you convert from degrees to radians?

Answer 16

Think of the 180 being in units of degrees and the pi being in units of radians

Question 17

What is the equation for the cirfumference of a circle?

Answer 17

Question 18

What do the letters represent in this equation?

Answer 18

Question 19

What is the equation for the linear speed around the circumference of a circle?

Answer 19

Question 20

What do the letters represent in this equation?

Answer 20

Question 21

Define angular speed.

Answer 21

Is the angle an object moves through unit time.

Question 22

What do the letters represent in this equation?

Answer 22

Question 23

What other equation(s) can angular speed be written in?

Answer 23

Can you see the similarities with linear speed?

Question 24

What do the letters represent in this equation?

Answer 24

Question 25

What are the conditions for SHM?

Answer 25

Acceleration is directly proportional **and** in the opposite direction to displacement.

Question 26

What is the constant of proportionality in the SHM condition?

Answer 26

Question 27

What is the displacement of an object undergoing SHM?

Answer 27

Question 28

What do the letters represent in this equation?

Answer 28

Question 29

What is the velocity of an object undergoing SHM?

Answer 29

Question 30

What do the letters represent in these equations?

Answer 30

Question 31

What is the acceleration of an object undergoing SHM?

Answer 31

## Footnote And force would be this multiplied by m.

Question 32

What do the letters represent in these equations?

Answer 32

Question 33

What does it mean for an object to *oscillate*? | (To move in SHM)

Answer 33

Object moves, repeatedly, one direction then in the opposite direction through its equilbrium position.

Question 34

Why do we refer to the resultant force in SHM as the *restoring* force?

Answer 34

Because it wants to *restore* equilibrium. | Hence it always points towards the equilibrium position.

Question 35

What are the 2 main examples of a Simple Harmonic Oscillator?

Answer 35

1. Mass-spring system 2. Simple pendulum

Question 36

What is the graident of a velocity-time graph?

Answer 36

Acceleration.

Question 37

What is the restoring force in a mass-spring system?

Answer 37

## Footnote aka Hooke's law

Question 38

What do the letters represent in this equation?

Answer 38

Question 39

What is the equation for maximum speed?

Answer 39

Question 40

What do the letters represent in this equation?

Answer 40

Question 41

What is the restoring force in a simple pendulum?

Answer 41

Question 42

What do the letters represent in this equation?

Answer 42

Question 43

What is the equation for maximum acceleration?

Answer 43

Question 44

What do the letters represent in this equation?

Answer 44

Question 45

Why are both these restoring forces negative?

Answer 45

Because they act in the opposite direction to the displacement. | ie they act towards the equilibrium position.

Question 46

Where in an oscillation does the maximum speed occur?

Answer 46

At the equilibrium position.

Question 47

What are the frequency and time period equations for the mass-sping system?

Answer 47

Question 48

What do the letters represent in this equation?

Answer 48

Question 49

Where in an oscillation does the zero speed occur?

Answer 49

At maximum displacement (Amplitude).

Question 50

What are the frequency and time period equations for the simple pendulum?

Answer 50

Question 51

What do the letters represent in this equation?

Answer 51

Question 52

Where in an oscillation does the maximum acceleration occur?

Answer 52

At maximum displacement (Amplitude).

Question 53

Is the time period of a mass-spring system independent of gravity?

Answer 53

Yes. | Gravity doesn't appear in the equation

Question 54

Where in an oscillation does zero acceleration occur?

Answer 54

At the equilibrium position.

Question 55

Is the time period of a simple pendulum independent of amplitude?

Answer 55

Yes. | Amplitude does not appear in the equation (but only for small angles).

Question 56

What is the equation for elastic potential energy for a mass-spring system?

Answer 56

Question 57

What do the letters represent in this equation?

Answer 57

Question 58

What is the equation for maximum elastic potential energy for a mass-spring system? | and hence total energy

Answer 58

Question 59

What do the letters represent in this equation?

Answer 59

Question 60

Using the previous 2 equations, give an equantion for KE.

Answer 60

Question 61

What do the letters represent in this equation?

Answer 61

Question 62

Draw a graph of energy vs displacement with KE, EPE, and total energy.

Answer 62

Question 63

Draw a graph of energy vs time with KE and EPE.

Answer 63

Question 64

Define damping.

Answer 64

When an oscillating system loses energy. Resulting in lessened amplitude.

Question 65

What are the 4 types of damping?

Answer 65

1. Light damping 2. Heavy damping 2. Critical damping 3. Over damping

Question 66

What is light damping?

Answer 66

When the amplitude is gradually decreased by a small amount each oscillation.

Question 67

What is heavy damping?

Answer 67

When the amplitude is decreased by a larger amount each oscillation.

Question 68

What is critical damping?

Answer 68

When the amplitude is reduced to zero in the shortest possible time (without oscillating).

Question 69

What is over damping?

Answer 69

When the amplitude is reduced slower than with critical damping, but without any oscillations.

Question 70

Define free vibrations?

Answer 70

Involve no energy trasfer to or from surroundings. The oscillator will oscillate at its natural/resonant frequency.

Question 71

Define force vibrations?

Answer 71

Involve an external driving force, driving an oscillator at a specific driving frequency.

Question 72

Define resonance.

Answer 72

Is when the driving frequency appraoches the natural frequency. The oscillator gains more enegry and hence oscillates with increasing amplitude.

Question 73

What does a resonance graph look like?

Answer 73

Question 74

What effect does damping have on a resonance curve?

Answer 74

The curve becomes blunted, and the resonant frequency drifts lower than the natural frequency.