Circular Motion Flashcards
When an object has uniform circular motion what does that mean?
A constant linear speed
Why must an object in circular motion must be accelerating and which direction does it act in?
It is continuously changing direction. Since velocity is the speed in a given
direction, it, therefore, has a constantly changing velocity
The object therefore must be accelerating
This is because acceleration is defined as the rate of change of velocity.
This acceleration is called the centripetal acceleration and is perpendicular to the
direction of the linear speed.
Draw a diagram with Force, acceleration and tangential speed for an object in circular motion
Provided in the document
What causes centripetal acceleration and what direction does it act in?
The centripetal acceleration is caused by a centripetal force of constant magnitude that
also acts perpendicular to the direction of motion (towards the centre)
Therefore, the centripetal acceleration and force act in the same direction.
What is the definition for angular displacement?
The change in angle, in radians, of a body as it rotates around a circle.
What is the equation for angular displacement?
Δθ= Δs/r
Δθ = angular displacement, or angle of rotation (radians)
s = length of the arc, or the distance travelled around the circle (m)
r = radius of the circle (m)
What is the definition of angular speed?
The rate of change in angular displacement with respect to time.
What is the equation for angular speed?
In terms of angular displacement
⍵= Δθ/Δt
⍵ = angular speed (rad s-1)
Δθ = change in angular displacement (radians)
Δt = time interval (s)
What is the equation for angular speed in terms of linear speed?
⍵= v/r
⍵ = angular speed (rad s-1)
v = linear speed (m s-1)
r = radius of orbit (m)
What is the equation for angular speed in terms of frequency?
⍵= 2πf
⍵ = angular speed (rad s-1)
f = frequency (Hz)
What is the equation for angular speed in terms of time period?
⍵= 2π/T
⍵ = angular speed (rad s-1)
T = the time period (s)
What is angular speed the same as?
Angular velocity is the same as angular speed, but it is a vector quantity.
What is the defintion for centripetal acceleration?
The acceleration of an object towards the centre of a circle when an object
is in motion (rotating) around a circle at a constant speed.
What is the equation for centripetal acceleration in terms of linear speed and radius?
a = v^2/r
a = centripetal acceleration (m s-2)
v = linear speed (m s-1)
r = radius of the orbit (m)
What is the equation for centripetal acceleration in terms of angular speed and linear speed?
a= v⍵
a = centripetal acceleration (m s-2)
v = linear speed (m s-1)
⍵ = angular speed (rad s-1)
r = radius of the orbit (m
What is the definition for centripetal force?
The resultant perpendicular force towards the centre of the circle required
to keep a body in uniform circular motion.
What is the equation for centripetal force?
F=mv^2/r=mr⍵^2=mv⍵
F = centripetal force (N)
v = linear velocity (m s-1)
⍵ = angular speed (rad s-1)
r = radius of the orbit (m)
Draw a diagram for an object in circular motion with angular sped, linear speed, the radius and F
Provided in the document
Why does centripetal force and acceleration act in the same direction?
Due to Newton’s second law
What do you have to remember about centripetal force?
The centripetal force is not a separate force of its own
It can be any type of force, depending on the situation, which keeps an object moving
in a circular path.
What are some situations and the centripetal force within them?
Car travelling about a roundabout - Friction between car types and the road
Ball attached to a rope moving in a circle - Tension in the rope
Earth orbiting the Sun - Gravitational force
