Unit 3.1 Circular Motion

Question 1

Define radian
(2-way)

Answer 1

• An angle such that
• the arc length = radius of the circle

Question 2

Why does the radian have no unit?

Answer 2

It’s a ratio of two lengths

Question 3

Hence, the equation for finding the radian in a sector of a circle?
(Not in data booklet)

Answer 3

θ = c/r

Question 4

Define θ?
(Finding radian in a circle)

Answer 4

Radian…
(No unit/rad)

Question 5

Define c?
(Find radian in a circle)

Answer 5

Circumference
or
Arc length
(m)

Question 6

Define r?
(Find radian in a circle)

Answer 6

Radius
(m)

Question 7

How to convert between radians and degrees
(Basic principles)
(3-way)

Answer 7

• 360° in one revolution of a circle
• corresponding to 2π radians

2π = 360°

Question 8

Degree to radians?

Answer 8

Deg x π/180

Question 9

Radians to degree?

Answer 9

Rad x 180/π

Question 10

But then, what’s the equation for finding the arc length?
(Noot in data booklet)

Answer 10

Arc length c = rθ

Question 11

Define angular velocity ω
(3-way)

Answer 11

• Suppose an object moves with
• constant motion through an angle θ
• in a time t

Question 12

Therefore, angular velocity equation?
(In data booklet)

Answer 12

ω = θ/t

Question 13

Define ω?
(Angular velocity eqn)

Answer 13

Angular velocity
(rads^-1)

Question 14

Define θ
(Angular velocity eqn)

Answer 14

Angle in radians
(rad)

Question 15

Define t
(Angular velocity eqn)

Answer 15

Time in seconds
(s)

Question 16

What about angular velocity for one complete revolution?
(NOT IN DATA BOOKLET)

Answer 16

ω = 2π/T

Question 17

Define T?
(P_oint.E_vidence)

Answer 17

• Period
• Time taken for one revolution

Question 18

Define F?
(P_oint.E_vidence)

Answer 18

• N° of revolutions
• per unit time

Question 19

Hence, equation for number of revolutions?
(NOT IN DATA BOOKLET)

Answer 19

F = 1/T

Question 20

What can ω also be defined as?

Answer 20

Angular frequency

Question 21

Equation for angular frequency?
(NOT IN DATA BOOKLET, ofc)

Answer 21

ω = 2πf

Question 22

How can angular frequency be derived from?
(3 by 3 steps)

Answer 22

• ω = 2π/T (aka “for 1 complete revolution”)
• ω = 2π/(1/F)
• ω = 2πf

Question 23

Equation for the instantaneous linear velocity V?
(in data booklet)

Answer 23

V = ωr

Question 24

Define V
(Instantaneous linear velocity eqn)

Answer 24

… instantaneous velocity
(ms^-1)

Question 25

Define ω
(Instantaneous linear velocity eqn)

Answer 25

Angular velocity
(rads^-1)

Question 26

Define r
(Instantaneous linear velocity eqn)

Answer 26

Radius
(m)

Question 27

Show that V = ωr?
(Whiteboard)
(5-way)

Answer 27

• The diagram, then:
• V = d/t
• = c/t
• = rθ/t
• HENCE, V = ωr

Question 28

Define centripetal acceleration a?
(4-way)

Answer 28

• When an object moves with constant motion,
• in a circle it must be
• accelerating even though
• ω is constant

Question 29

3 jigs with centripetal acceleration?

Answer 29

• Acceleration is towards centre of circle
• Speed is constant
• Direction of velocity is always changing

Question 30

HENCE, eqn for centripetal acceleration?
(In data booklet)

Answer 30

a = V²/r

Question 31

Define a?
(Centripetal acceleration eqn)

Answer 31

… centripetal acceleration
(ms^-2)

Question 32

Define V²?
(Centripetal acceleration eqn)

Answer 32

Instantaneous velocity squared
(ms^-1)

Question 33

Define r?
(Centripetal acceleration eqn)

Answer 33

Radius of circle
(m)

Question 34

Show how centripetal acceleration can also be written as:
a = ω²r
(In data booklet actually)
(4-way)
(Whiteboard)

Answer 34

• a = V²/r
• = (ωr)²/r
• = ω²r
• Hence: a = ω²r

Question 35

What is meant by “centripetal force”?
(2-way)

Answer 35

• A force which acts on a body moving
• in a circular path

Question 36

Which direction does the centripetal force act?
Draw it too…. (Whiteboard)
(2-way)

Answer 36

• Directed towards
• the centre of the circle

Question 37

Centripetal force eqn w/ v?
(In data booklet)

Answer 37

F = mv²/r

Question 38

Centripetal force eqn w/ ω?
(In data booklet)

Answer 38

F = mω²r

Question 39

What’s the difference between 2 of the centripetal force eqn’s?
(Both in data booklet)

Answer 39

• One involves instantaneous velocity
• Other involves angular velocity

Question 40

Do u know some examples of centripetal force?
(THE, booklet)

Answer 40

Page 6… onwards

Question 41

This topic is heavily based on ppq….

Answer 41

… cuz it’s heavily based on problem solving