• Physics
(Grade 11 – general )
• Chapter 1
(rotational motion)
• Lesson 1
(describe rotational motion )
Part 1
• My objective is to describe angular displacement.
Linear motion
Displacement has a symbol (x)
Velocity has a symbol (v)
Acceleration has a symbol (a)
Δ𝑥
𝑣=
Δ𝑡
Δ𝑣
𝑎=
Δ𝑡
Angular motion
• Angular displacement has the symbol (θ)
• Angular velocity has the symbol (ω)
• Angular acceleration has the symbol (α)
Δθ
ω=
Δ𝑡
Δω
𝑎=
Δ𝑡
The relation between linear and angular motion
x = rθ
v = rω
a = rα
One complete
revolution equal
to
360 degree
or
2π radian
Radian and degree
π= 180 degree
2π = ?
π/2 = ?
π/4 = ?
3π/2 = ?
Radian and degree answers
π= 180 degree
2π = 360
π/2 = 90
π/4 = 45
3π/2 = 270
Check your understanding
Put the angles in radian and degree
answers
Earth rotation
example
• In 6 hours, how far will New York travel due to the rotation of
the Earth? The radius of the Earth is 6400 km.
example
• In 6 hours, how far will New York travel due to the rotation of
the Earth? The radius of the Earth is 6400 km.
• My objective is to calculate angular velocity.
Linear velocity
Angular Velocity
Calculating Speed
Check your understanding
example
• The Earth completes one rotation in 24 hours and has a radius of 6400 km. How fast
does a point on the Earth's equator revolve around the center of the Earth?
example
• The Earth completes one rotation in 24 hours and has a radius of 6400 km. How fast
does a point on the Earth's equator revolve around the center of the Earth?
Check your understanding
Check your understanding
exercise
Angular Frequency
• The unit of frequency is Hz
example
example
• My objective is to calculate angular acceleration.
example
• A CD is spun from rest to an angular velocity of 50 rad/s in 1.5
s. What was the average angular acceleration of the CD?
example
• A CD is spun from rest to an angular velocity of 50 rad/s in 1.5
s. What was the average angular acceleration of the CD?
Practice
Linear acceleration
Example
A cyclist accelerates at 0.85 m/s2. The wheels of his bike have a radius of 35 cm. What is the angular
acceleration of the wheels?
Example
A cyclist accelerates at 0.85 m/s2. The wheels of his bike have a radius of 35 cm. What is the angular
acceleration of the wheels?
practice
•summarize what did we learn
Linear motion
Displacement has a symbol (x)
Velocity has a symbol (v)
Acceleration has a symbol (a)
Δ𝑥
𝑣=
Δ𝑡
Δ𝑣
𝑎=
Δ𝑡
Angular motion
• Angular displacement has the symbol (θ)
• Angular velocity has the symbol (ω)
• Angular acceleration has the symbol (α)
Δθ
ω=
Δ𝑡
Δω
𝑎=
Δ𝑡
The relation between linear and angular motion
x = rθ
v = rω
a = rα
Sammury
Extra resources
• Lms 1 :
https://edushare.moe.gov.ae/Uploads/Resources/e60a7b9d5faf-497e-8d5d-89af847deda2/11803160/index.html